Medical maths calculators
Find the clinical calculation you need without digging through unnecessary clutter. Search directly, jump to a popular calculator, or choose the problem that matches the task in front of you.
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What are you trying to work out?
Choose the statement that looks most like the order, values, or problem in front of you.
I need a square root, power, percentage or general calculation.
Use the scientific calculator for brackets, roots, powers, logs, trigonometry and everyday arithmetic.
My order is in mg. How many mL do I give?
Use the prescribed mg dose and the strength on the medicine label.
My order is mg/kg. How many mL per dose?
Use the mg/kg order, patient weight, and liquid strength.
I need to turn a dose into tablets.
Use the prescribed dose and the strength of one tablet.
I have a volume and time. What mL/hr do I set?
Calculate the pump rate directly. No drop factor is needed.
I have mL/hr. What gravity drip rate do I set?
Use the ordered rate and the drop factor printed on the giving set.
I know the volume and mL/hr. How long will it take?
Calculate duration and, if needed, the estimated finish time.
My reference says Cockcroft-Gault CrCl.
Calculate adult creatinine clearance using the weight method specified by the reference.
My reference says CKD-EPI eGFR.
Calculate the 2021 CKD-EPI creatinine estimate and view the G category as context.
I need BSA, IBW, or adjusted body weight.
Open the body-measures hub and choose the measure named by the protocol.
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Browse by calculation area
Open a topic when you know the clinical area but not the exact calculator name.
General & Scientific
Work through square roots, powers, brackets, percentages, logarithms, trigonometry and everyday arithmetic.
Open calculatorDose Calculations
Start with the medication order and label: find mL from mg, mg/kg, or units without pre-calculating the answer first.
Browse topicTablet Dosing
Calculate tablets from fixed or weight-based doses with unit matching and kg/lb support.
Open calculatorFluid Balance
Total recorded intake and output volumes and compare them to give a fluid balance, with the working shown.
Open calculatorIV Fluids & Infusions
Choose by the answer you need: pump rate in mL/hr, gravity drops/min, infusion duration, or a check of an existing drip.
Browse topicDilutions & Concentration
Choose between C1V1=C2V2 dilution arithmetic and a verified-input final IV bag concentration check. Use mg to mL for vial withdrawal volume.
Browse topicDosing Body Measures
Calculate BSA, Devine ideal body weight, or the 0.4 adjusted-body-weight method when a protocol specifically names that measure.
Browse topicRenal Dosing Support
Start with modern CKD-EPI 2021 eGFR or use Cockcroft-Gault CrCl when a current source specifically requires it.
Browse topicLab Calculators & Corrections
Laboratory calculation tools for corrected calcium, corrected sodium, anion gap, serum osmolality and osmol gap.
Browse topicPaediatric Nursing
Paediatric nursing calculators and guides for weight-based medication maths, maintenance fluids, tablet dosing and BSA.
Open calculatorComplete directory
All medical maths calculators
Every calculator remains listed below in normal crawlable links. Jump to a category or scan the full directory.
General & Scientific
1- mg to mL CalculatorUse when the order is in mg and the liquid strength is in mg/mL or mg per X mL.
- mg/kg to mLUse when a liquid medicine order is written in mg/kg per dose or mg/kg/day and weight is documented in kg or lb.
- Units to mL CalculatorUse when both the order and product strength are expressed in units.
Tablet Dosing
1Fluid Balance
1- IV Drip RateUse when the giving-set drop factor is known and the order provides either mL/hr or total volume and time.
- Volume + time → mL/hrUse when the order says a volume over a time and you need the mL/hr pump rate. No drop factor is required.
- Observed gtt/min → mL/hrUse only when the gravity drip is already running and you counted whole drops over one full minute, or made a quick 15-second whole-drop count, with the exact giving-set drop factor.
- mcg/kg/minUse when programming or verifying a weight-based infusion of a vasoactive, sedative, or inotropic agent in mcg/kg/min.
- Infusion Time CalculatorUse when you know the volume to infuse and mL/hr rate and need to know how long it will take or when it will finish.
- BSA CalculatorUse when a protocol or calculation requires body surface area in m² and a named BSA equation.
- Ideal Body WeightUse when a medicine reference or protocol requires adult clinical ideal body weight; Devine is the primary MedMaths method and named alternatives should be followed when specified.
- Adjusted Body WeightUse only when a medicine reference, equation, or local protocol specifically requires the 0.4 adjusted-body-weight method.
- Corrected CalciumUse when reproducing or interpreting an albumin-adjusted calcium value; a 2026 international laboratory position statement recommends against routine laboratory reporting of corrected calcium.
- Anion GapUse when you need the potassium-free anion-gap arithmetic, with optional albumin adjustment, for comparison with the reporting laboratory reference interval.
- Serum OsmolalityUse when you need calculated serum osmolality or, with a measured value, the numeric measured-minus-calculated osmol gap.
- Corrected SodiumUse when a current source asks for a Katz or Hillier hyperglycaemia-adjusted sodium estimate from measured sodium and glucose.
Common calculation types
Medication dose calculations
Use these when a medication order must be converted into a measurable amount, such as mL, tablets, or units.
IV fluid and drip rate calculations
Use these when the question involves mL/hr, drops per minute, drop factor, or the time left for an IV bag.
Medication dilution and IV concentration calculations
Use these when the problem involves stock concentration, final total volume, or a final IV concentration check. Use mg to mL for vial withdrawal volume.
Dosing body measures and renal support
Use these when a medicine calculation or reference specifically requires BSA, ideal body weight, or Cockcroft-Gault creatinine clearance.
Medical maths calculator FAQs
What is MedMaths?
MedMaths is a medical maths calculator website for medication calculations, IV fluid maths, dilutions, body measure calculations, and renal dosing support.
- It is designed to show the formula, calculation steps, and answer clearly.
- The calculators are educational arithmetic tools and do not decide whether a dose is clinically appropriate.
A typical MedMaths calculation is 250 mg ÷ 50 mg/mL = 5 mL.
Which medical maths calculator should I use?
Choose the calculator that matches the units in the question: mg/mL for liquid doses, mg/kg for weight-based doses, gtt/min for drops, and C1V1 for dilution arithmetic.
- If the order is in mg and the label is in mg/mL, use mg to mL.
- If the order is in mg/kg, calculate the total dose from weight first.
- If the problem mentions drop factor, drops per minute, or mL/hr, use an IV calculator.
500 mg ordered with 250 mg tablets uses mg to tablets, not mg to mL.
What calculators are included on MedMaths?
MedMaths includes calculators for dose calculations, tablet dosing, IV fluids, dilutions, BSA, ideal body weight, and creatinine clearance.
- Dose calculators include mg to mL, mg/kg to mL, and units to mL.
- IV calculators include mL/hr to gtt/min, gtt/min to mL/hr, and infusion time.
- Dilution calculators include C1V1=C2V2 and reconstitution to IV bag. Vial withdrawal volume is handled by the mg-to-mL calculator.
There are 23 calculator pages across 10 medical maths topics.
Are MedMaths calculators for nurses and students?
Yes. The calculators are written for medication maths practice, nursing calculation revision, and clinical arithmetic support.
- The pages include formulas, worked examples, FAQs, and practice questions.
- They are useful for checking calculation logic, but they do not replace local medication policy or clinical judgement.
- High-risk medicines should still be checked according to local requirements.
For an IV rate problem, the page shows both the formula and the worked calculation.
Are these calculators medical advice?
No. MedMaths calculators are arithmetic and education tools only.
- They do not prescribe, recommend, or validate medication doses.
- Always check the order, product label, route, patient factors, maximum dose limits, compatibility, and local policy.
- If the answer looks unexpected, stop and recheck the units before using the result.
The calculator can show 20 units ÷ 100 units/mL = 0.2 mL, but it cannot decide whether 20 units is the correct dose.
Continue with MedMaths
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Learn the maths
Work through medication maths and clinical calculations step by step.
Open LearnRead a calculation Guide
Understand the formula, worked method, limitations and evidence behind the arithmetic.
Browse GuidesBrowse by specialty
See calculators and learning resources grouped around common clinical areas.
Browse specialtiesInterested in where named clinical equations came from? Explore Formula History →
Check the calculation, then check the clinical context
MedMaths shows the arithmetic and working. Confirm the medication order, product strength, units, route, patient factors, maximum dose limits, compatibility, independent-check requirements and local policy before clinical use.