Medical calculators
Free, no-signup calculators for the numbers behind safe prescribing. Each one runs entirely in your browser, stores nothing, and is built on a published formula with every constant cited to its primary authority — the CDC, the National Kidney Foundation, and the original clinical literature.
Creatinine clearance (Cockcroft-Gault)
Estimate kidney function for renal drug dosing from age, sex, weight and serum creatinine.
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eGFR (CKD-EPI 2021)
The race-free 2021 equation labs use to stage kidney function, from age, sex and creatinine.
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Ideal body weight (Devine)
The reference weight behind many weight-based drug doses — from sex and height.
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Opioid MME calculator
Total daily morphine milligram equivalents across opioids, using the CDC conversion factors.
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Steroid (corticosteroid) conversion
Convert between prednisone, dexamethasone, hydrocortisone and others by anti-inflammatory potency.
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How long a drug stays in your system
Time to essentially clear a drug from plasma, from its half-life (about 5 half-lives).
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BMI calculator
Body Mass Index and weight category from height and weight, with the FDA weight-drug cutoffs.
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QTc calculator (Bazett & Fridericia)
Correct the QT interval for heart rate — relevant to QT-prolonging medications.
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Body surface area (Mosteller)
Estimate BSA from height and weight — the number behind chemotherapy and other weight-based doses.
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Albumin-corrected calcium
Adjust total serum calcium for a low albumin, so a normal calcium isn't mistaken for a low one.
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Serum anion gap
Na − (Cl + HCO3), with albumin correction — a high gap points to a metabolic acidosis.
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These tools give estimates for general information and education. They are not a substitute for a clinician’s judgment, a laboratory-reported result, or an individualized dosing decision. Always confirm with a pharmacist or prescriber before acting on any number here.