Veterinary Calculators for Vets and Nurses
37 free clinical calculators. No login, no app to install, no trial that expires. Built by Dr Duncan Houston, an emergency veterinarian, to work one-handed on a phone propped against a kennel door.
Anaesthetic and emergency drug doses, constant rate infusions, IV fluid rates, blood gas and anion gap, sodium and phosphate correction, transfusion volumes, CPR cycle timing, trauma triage, MGCS, IRIS staging and IVDD grading. Every calculator shows its full working and names the guideline or method behind it, and every formula is published on this page.
Quick answer
Search or filter below, or start from the clinical job in the categories further down. These assume clinical training and are written for veterinary professionals. Owners should use the free pet calculators for owners instead.
In a crash
The ones you want already open when it goes bad. Bookmark this page or add it to your home screen.
Jump back in
All 37 veterinary calculators, A to Z
Albumin Dose Calculator
Albumin deficit or g/kg dosing for hypoalbuminaemia, with volumes for human 25%, 20%, 5% and canine albumin, infusion rate, predicted response and the reaction and overload cautions built in.
Basis: Basis: Deficit (g) = 10 x (target minus current albumin, g/dL) x kg x 0.3, capped at 2 g/kg per day; product volumes and rates from published canine and feline protocols and manufacturer labelling
Anaesthetic, Sedation & Analgesia Drug Calculator
40 drugs and 4 combination protocols for dogs and cats, with editable vial concentrations, patient risk flags, interaction checks and printable cage sheets.
Basis: AAHA Anesthesia & Monitoring (2020) and Pain Management (2022) guidelines
Anaesthetic Risk Estimator
Understand your pet's anaesthetic risk before surgery or a dental, and the questions worth asking your own vet beforehand.
Basis: This tool produces a non-validated educational planning score from 1 to 10.
Antibiotic Dose & Choice Calculator
Empirical antibiotic selection when you do not have a culture and sensitivity yet: pick the species and the presentation, and get the stewardship-ranked first choice.
Basis: The dose at your patient’s weight, when culture is non-negotiable, and the warnings that actually matter.
Antihistamine Dose Calculator
Weight-based doses of single-ingredient antihistamines for dogs and cats, and why most allergy packets on the shelf must never be given.
Basis: Safe starting doses for diphenhydramine, cetirizine, loratadine, chlorphenamine, fexofenadine and clemastine.
Antithrombotic Calculator: When and Which to Use
Decide whether a dog or cat needs antithrombotic therapy, choose between antiplatelets and anticoagulants, and get weight-based doses with monitoring and stopping guidance.
Basis: Doses follow the CURATIVE consensus (J Vet Emerg Crit Care 2019) as summarised for clinical use.
Blood Gas Calculator
Interpret arterial and venous blood gas results with anion gap, base excess and an expected-compensation check.
Basis: Anion gap = (Na + K) - (Cl + HCO₃), with expected-compensation check
Blood Transfusion Volume Calculator
Volume of packed red cells or whole blood to reach a target PCV, plasma volumes for coagulopathy, plus rate and monitoring milestones.
Basis: Weight × blood volume factor (~90 mL/kg dog, ~60 mL/kg cat) × PCV gap ÷ donor PCV
Caesarean Planning Calculator
Timing, drug selection and preparation planning for an elective or emergency caesarean.
Basis: Progesterone drop and gestation-length timing
Canine Pain Calculator
A validated behaviour-based tool for assessing acute pain in dogs.
Basis: A pictorial 0–4 scale for acute pain in dogs. Scores of 2 and above prompt a reassessment of the analgesic plan.
Chinese Herbal Medicine (TCVM) Dose Calculator
Granule and powder dosing for 174 formulas and single herbs across 9 species, with patient risk flags and traditional contraindication lists.
Basis: Chi University / Jing Tang dosing convention. A supplier convention, not an efficacy evidence base
Constant Rate Infusion (CRI) Calculator
CRI concentrations, fluid bag additions and pump rates, with a printable infusion label.
Basis: mL/hr = mcg/kg/min × kg × 60 ÷ concentration in mcg/mL
Constipation, Megacolon & Colonoscopy Prep Calculator
Weight-based PEG 3350 treatment plans for feline deobstipation, dog and cat colonoscopy bowel prep, maintenance laxative dosing and the in-house PEG electrolyte solution recipe.
Basis: This tool doses in-hospital treatments: nasogastric lavage, IV maropitant and enemas. Pet owners: if your dog or cat is straining, not passing faeces or vomiting, please see your vet.
Corrected Chloride Calculator
Correct the measured chloride for changes in free water and sodium, so you can tell a true chloride disturbance from a water problem in one step.
Basis: This tool interprets serum or plasma chloride against sodium. It supports, and never replaces, blood gas analysis and clinical judgement.
CPR Timer
Two-minute cycle timer with compressor swap prompts, drug interval reminders and a running event log.
Basis: RECOVER CPR cycle structure
Daily Calorie Calculator
How many calories your dog or cat actually needs each day, from resting energy requirement adjusted for age, desexing and activity.
Basis: Estimate your animal's daily calories, resting energy requirement (RER) and food portions in grams, cups or meals.
Dilution Calculator
Enter what is on the vial, what you need and the final volume. Works in %, mg/mL, mcg/mL, g/L, mEq/mL, IU/mL and ratio strengths.
Basis: C1V1 = C2V2, with safer bag, reverse-check and serial-dilution workflows.
DKA vs HHS Calculator
Separate diabetic ketoacidosis from hyperosmolar hyperglycaemic state, with corrected sodium and effective osmolality.
Basis: Effective osmolality = 2 × Na + glucose (mmol/L); glucose-corrected sodium
Emergency Drug Calculator
Crash-cart doses and draw-up volumes by body weight for the drugs you reach for first, all on one screen.
Basis: Standard emergency dose ranges, RECOVER-aligned for arrest drugs
Emergency Vet Triage Questions: What to Ask Before the Consult
A structured triage tool for veterinary nurses and reception staff.
Basis: Trained veterinary nurses, technicians and reception staff triaging patients that have already arrived at a clinic.
Feline Pain Scale Calculator
Four validated feline pain tools in one
Basis: CSU: holistic 0–4. Feline Grimace Scale: 5 facial units, /10 (treat ≥4). UNESP-Botucatu MCPS: 10 items, /30 (treat ≥8). Glasgow CMPS-Feline: 7 questions, /20 (treat ≥5)
Glucose Curve & Insulin Dose Calculator
Plot a blood glucose curve, identify nadir and duration, and work through the next insulin dose adjustment.
Basis: Nadir, duration and insulin overlap assessment
Hospital Cage Card Generator
Add patient identification, CPR or DNR status, behaviour, isolation precautions, diet, NPO instructions and essential nursing alerts, then print it for the cage, kennel, ward, ICU or isolation area.
Basis: Create a clear, printable veterinary cage card for a dog or cat in hospital.
Hospital Handover (I-PASS)
Type each patient's case notes during the shift, then print or copy a clean I-PASS handover for the next vet. Patients sort sickest first within each department and your draft auto-saves in this browser.
Basis: I-PASS uses five core elements: Illness severity, Patient summary, Action list, Situation awareness and contingency planning, and Synthesis by receiver.
Hospital Patient Chart
Vitals and care tasks on top, medications and IV fluids below, every due time highlighted so nothing gets missed.
Basis: Daily cage sheet with automatic dose calculations.
IRIS Kidney Disease Staging Calculator
Stage and substage chronic kidney disease on creatinine and SDMA, with proteinuria and blood pressure substaging.
Basis: IRIS CKD staging guidelines
IV Drug Compatibility Checker
Which injectable drugs and fluids can share one IV line, catheter lumen or bag in a hospitalised dog or cat.
Basis: "Compatible" means physically compatible at usual concentrations for a brief Y-site contact; results depend on concentration, diluent, pH and brand.
IV Fluid Calculator
Maintenance, dehydration deficit and ongoing losses combined into a single hourly rate, with drip and pump settings.
Basis: Maintenance + deficit (% dehydration × kg × 10 mL) + ongoing losses
IV Fluid Therapy Calculator
The calculator recommends the best-fit IV fluid, calculates the fluid rate, plans shock boluses, and doses common bag additives and electrolyte corrections for the actual patient and bag size.
Basis: Enter a patient's blood results, hydration status and clinical signs.
Modified Glasgow Coma Scale Calculator
Score motor activity, brainstem reflexes and level of consciousness for a head trauma prognosis.
Basis: Modified Glasgow Coma Scale (MGCS): three categories scored 1 to 6, total 3 to 18
Phosphate Supplementation Calculator
Potassium phosphate infusion rates for hypophosphataemia, with the calcium and potassium cautions built in.
Basis: mmol/kg/hr phosphate infusion with combined potassium load check
Pre-Surgical Checklist
Enter the admission time and this tool works out exactly when food and water stop, builds a morning medication plan and gives you a tick-off list for the night before and the morning of surgery.
Basis: No medications listed. If your pet takes anything at all, including supplements or flea and worm products, tell the clinic.
Pregnancy & Due Date Calculator
Work out gestation stage, the whelping or queening date and what to prepare when, from the mating dates you have.
Basis: Pick the species, enter one date, and get an estimated birth date plus a full pregnancy timeline.
Sodium Correction Calculator
Safe rates of change for hyponatraemia and hypernatraemia, with free water deficit and the fluid choice to get there.
Basis: Chronic or unknown duration: 0.5 mmol/L/hr and 10 to 12 mmol/L/24 hr ceilings. Acute cases branch separately
Trauma Triage Score Calculator
Animal Trauma Triage score across six categories, to grade severity and estimate survival on presentation.
Basis: Animal Trauma Triage (ATT): six categories scored 0 to 3, total 0 to 18
Unit Converter
Veterinary unit conversions in both directions: SI and conventional, weights, doses, glucose, creatinine and more.
Basis: SI and conventional unit conversion factors
Veterinary IVDD & Spinal Staging Calculator
Grade spinal injury from pain only through to loss of deep pain sensation, with prognosis and surgical urgency.
Basis: Modified Frankel / Griffiths 1 to 5 grading
Free, and staying free
No account, no trial, nothing gated, nothing to install. If a calculator saves you a phone call at 2am, that is the whole point. If something is wrong, out of date, or you want one that does not exist yet, tell me and I will build it.
Sending an owner home with instructions?
The owner-facing tools cover toxicity thresholds, feeding amounts, quality of life scoring, vaccination schedules and prevention. Safe to hand out as a link in a discharge email.
Why these veterinary calculators exist
Most veterinary calculators online are either a decade-old spreadsheet in a browser or a paywalled app that wants your email before it will multiply two numbers. These are neither. They are free, they show their working, and they are built to be readable at arm's length on a phone propped against a kennel door while your hands are busy.
Each calculator states the guideline or method it follows on its card, and several are built directly on published guidance including the AAHA anaesthesia and pain management guidelines, RECOVER CPR and IRIS staging criteria. They are decision support. The dose you give is your clinical decision, on your patient, under your registration.
Spelling note for searchers: this page uses Australian spelling. An anaesthetic drug calculator is the same thing as an anesthetic drug calculator, haematology is hematology, and hypophosphataemia is hypophosphatemia.
Start from the clinical job
If you know the tool, search for it. If you are working from the patient instead, start here.
| Clinical job | Calculators |
|---|---|
| Anaesthesia and analgesia | Anaesthetic, Sedation & Analgesia Drug Calculator with cage sheet mode, Constant Rate Infusion (CRI) Calculator |
| Emergency and critical care | CPR Timer, Emergency Drug Calculator, Blood Transfusion Volume Calculator |
| Fluids, electrolytes and acid–base | IV Fluid Calculator, Blood Gas Calculator, Sodium Correction Calculator, Phosphate Supplementation Calculator |
| Scoring and staging | Trauma Triage Score, Modified Glasgow Coma Scale, IRIS Kidney Disease Staging, IVDD & Spinal Staging |
| Endocrine and metabolic | DKA vs HHS Calculator, Glucose Curve & Insulin Dose Calculator |
| Reproduction | Caesarean Planning Calculator |
| Reference | Unit Converter |
The formulas behind each calculator
Published as text rather than hidden inside a widget, so you can sanity-check a result, hand the working to a student, or do it on paper when the wifi drops.
How do you calculate a CRI rate?
Millilitres per hour = dose (mcg/kg/min) × body weight (kg) × 60 ÷ concentration (mcg/mL). The CRI calculator also solves the fluid-bag form, where a known drug volume is added to a bag running at a set rate, and it prints an infusion label so the bag is not a mystery to the next shift.
How do you calculate an IV fluid rate?
Hourly rate = maintenance + deficit + ongoing losses, where the deficit in mL = percent dehydration × body weight (kg) × 10, spread over your chosen replacement window. Drip rate in drops per minute = mL/hr × giving-set drop factor ÷ 60. The fluid calculator returns both the pump setting and the drip count.
How do you calculate a transfusion volume?
Volume (mL) = body weight (kg) × blood volume factor × (target PCV − patient PCV) ÷ donor PCV, with the blood volume factor around 90 mL/kg in dogs and 60 mL/kg in cats. Plasma is a different calculation entirely: it is dosed per kilogram for coagulopathy, never to a PCV target, because it carries no red cells. The transfusion calculator handles both and adds rate and monitoring milestones.
How fast can you correct sodium?
For chronic or unknown-duration cases, no faster than 0.5 mmol/L/hr and no more than 10 to 12 mmol/L in 24 hours. The 24-hour ceiling is the one that predicts osmotic demyelination, and it binds independently of the hourly rate. Documented acute hyponatraemia with neurological signs is a different situation and warrants deliberate partial correction. Free water deficit = 0.6 × body weight (kg) × ((patient Na ÷ target Na) − 1). The sodium calculator branches acute and chronic separately.
How do you calculate anion gap and effective osmolality?
Anion gap = (Na + K) − (Cl + HCO₃). Effective osmolality = 2 × Na + glucose, in mmol/L. Corrected sodium adds 1.6 mmol/L for every 5.5 mmol/L (100 mg/dL) that glucose sits above normal. The blood gas calculator adds base excess and an expected-compensation check; the DKA vs HHS calculator uses the osmolality and corrected sodium to separate the two syndromes.
How are the MGCS and ATT scored?
The Modified Glasgow Coma Scale scores motor activity, brainstem reflexes and level of consciousness from 1 to 6 each, for a total of 3 to 18, where lower is worse. The Animal Trauma Triage score uses six categories scored 0 to 3 each, for a total of 0 to 18, where higher is worse. Both are on this page: MGCS and ATT.
How is IVDD graded, and how is CKD staged?
IVDD uses the modified Frankel and Griffiths grades 1 to 5, from spinal pain only through to loss of deep pain sensation. IRIS stages chronic kidney disease on fasting creatinine and SDMA, then substages on urine protein:creatinine ratio and systolic blood pressure. Grade 1 is pain without neurological deficit, which is the step most summaries skip. See IVDD grading and IRIS staging.
How do you calculate a drug volume from a dose?
Volume (mL) = dose (mg/kg) × body weight (kg) ÷ concentration (mg/mL). The concentration is the variable that catches people out, because vial strengths differ between manufacturers and countries. Every dosing calculator here lets you edit it, and you should read it off the bottle in your hand. Anaesthetic drug calculator.
How do you convert mg/dL to mmol/L?
Glucose: divide mg/dL by 18 to get mmol/L. Creatinine: multiply mg/dL by 88.4 to get micromoles per litre. Urea nitrogen to urea: multiply mg/dL by 0.357 for mmol/L. Every analyte has its own factor because the conversion depends on molecular weight, which is why a single blanket multiplier does not exist. The unit converter handles the common ones in both directions, which matters when you are reading a paper or a referral report written in the other system.
Which guidelines do these calculators follow?
The AAHA Anesthesia and Monitoring and Pain Management guidelines for the anaesthetic calculator, RECOVER for CPR cycle structure and arrest drugs, IRIS for chronic kidney disease staging, the Animal Trauma Triage score for trauma severity, the Modified Glasgow Coma Scale for head trauma, and modified Frankel and Griffiths grading for spinal injury. Each card names its basis so you can see it before you open the tool. Where a calculator follows a standard method rather than a named guideline, the card says that instead of implying a citation that does not exist.
A free alternative to the paid veterinary calculator apps
Almost everything else in this category is an app you install, or a site that is free until it is not. That model makes sense for the people building it and no sense at all for a nurse who needs a draw-up volume in the next ninety seconds, on a phone that is not theirs.
These pages are the other option. Nothing to download, nothing to log into, nothing that expires. Each calculator is a single self-contained page, so once it has loaded it keeps working if the clinic wifi drops. Add the page to your phone's home screen and it opens like an app without being one. Link them from your practice intranet if that is useful; no permission needed.
Using them safely in practice
Check the concentration, every time
The commonest source of error in a drug calculation is not the maths, it is the vial. Concentrations differ between manufacturers, countries and formulations. Read it off the bottle in your hand rather than trusting a default.
Read the working, not just the number
Each result shows the full calculation from the displayed operands, so a transposed weight or a wrong unit is visible rather than buried. If the working does not look like what you expected, stop.
Two-person checks still apply
A calculator does not replace a second pair of eyes on a controlled drug, a transfusion, or a paediatric or exotic dose. The anaesthetic calculator's cage sheet mode prints a signature line for exactly this reason.
These are not a substitute for a formulary
They calculate volumes and rates from doses you select. They do not know your patient's comorbidities, your practice protocols or your regional drug licensing. Cross-check against Plumb's or your own formulary for anything unfamiliar.
Species scope
Unless a calculator says otherwise it is written for dogs and cats. Exotics, equine and production species have different pharmacokinetics, different blood volume factors and different normal ranges, and scaling a canine figure to them is not safe.
Questions vets ask before using a calculator
Are these veterinary calculators actually free?
Yes. Every calculator is free, permanently, with no account, no trial and no email capture. There is nothing gated and no premium tier.
Is this an alternative to the paid veterinary calculator apps?
That is the intention. There is nothing to install, no login, and no free tier that expires. Each calculator is a single self-contained web page, so once loaded it keeps working without a connection, and you can add it to your phone's home screen for one-tap access.
How do you calculate a CRI rate?
Millilitres per hour equals the dose in mcg/kg/min multiplied by body weight in kilograms multiplied by 60, divided by the drug concentration in mcg/mL. The CRI calculator also solves the fluid-bag form, where a known volume of drug is added to a bag running at a set rate, and prints an infusion label.
How do you calculate an IV fluid rate?
Hourly rate equals maintenance plus the dehydration deficit spread over your chosen replacement window plus ongoing losses. The deficit in millilitres is percentage dehydration multiplied by body weight in kilograms multiplied by 10. Drip rate in drops per minute is mL/hr multiplied by the giving-set drop factor divided by 60.
Who built them and what are they based on?
Dr Duncan Houston, BVSc, University of Sydney, working in emergency and general practice. Each calculator states the guideline or method it follows, and several are built directly on published guidance including the AAHA anaesthesia and pain management guidelines, RECOVER CPR and IRIS staging criteria. The formulas themselves are published in full on this page.
Can nurses and technicians use these?
Yes, and they are designed with nurses in mind. Draw-up volumes, fluid rates, CRI tables and cage sheets are the daily nursing tasks these speed up. Prescribing decisions remain the veterinarian's.
Which species are these written for?
Dogs and cats unless the individual calculator says otherwise. Exotic, equine and production species have different pharmacokinetics, blood volume factors and normal ranges, and scaling a canine figure to them is not safe.
Do they work on a practice iPad or phone?
Yes. Each calculator is a single self-contained page with no backend, so once the page has loaded it keeps working even if the connection drops. Add it to your home screen on iOS or Android for one-tap access, though you will still need a connection for the first load each time.
Is anything I enter about a patient stored or sent anywhere?
No. Everything runs in your browser. No patient data is transmitted or stored on a server, which is deliberate given clinical record obligations. The only thing saved locally is which calculators you opened.
Can I print a calculation for the patient record?
Yes. Every calculator has a print stylesheet that strips the inputs and controls so you get a clean record of the calculation. The anaesthetic calculator also produces a printable cage sheet with time, given, initials and a two-person check line.
Can our clinic link to these or put them on our intranet?
Please do. Link freely to any calculator. If you want them embedded in a clinic system or branded for your practice, get in touch.
A dose or reference looks wrong. What do I do?
Contact me with the tool and the specific figure. Corrections from working clinicians get priority and I would rather fix it than defend it.