Health Calculators
Free, verified health calculators with step-by-step guides and reference data.
Adjusted Age Calculator — Corrected Age for Preemies
Calculate corrected (adjusted) age for a premature baby from birth date and gestational age at birth. See chronological vs. corrected age side by side.
Growth Percentile Calculator — BMI & Head Circumference
Find your child's CDC BMI-for-age or head-circumference-for-age growth percentile using the official LMS method. Boys and girls, birth to 20 years.
Menopause Age Calculator — Typical Range & Perimenopause Timeline
See where your age sits in the typical 45–55 menopause range, learn the perimenopause timeline, and get risk-factor context — not a personal prediction.
Odds Ratio Calculator — 2×2 Table with 95% CI
Calculate odds ratio and 95% confidence interval from a 2×2 table. Automatic continuity correction, Woolf's method CI, and plain-language interpretation.
DRI Calculator — Daily Reference Intake by Age & Sex
Find your daily RDA/AI for protein, fiber, vitamin C, vitamin D, calcium, iron, and potassium by sex, age bracket, and pregnancy/lactation status.
Caffeine Calculator — Content Tracker & Half-Life
Log drinks to track daily caffeine intake vs the FDA's 400 mg benchmark, or find how much caffeine remains in your system via the half-life formula.
Gestational Age Calculator — Due Date, Conception & Implantation
Calculate due date, conception date, and implantation window from your LMP using Naegele's Rule. See your current gestational age in weeks and days.
Water Fasting Calculator — Stage & Safety Guide
Find which physiological stage your planned water fast falls in, plus a prominent safety checklist and physician-supervision guidance for extended fasts.
AST/ALT Ratio Calculator — De Ritis Ratio
Calculate the AST/ALT ratio (De Ritis ratio) from your liver panel and see what the pattern typically suggests, alongside individual normal-range checks.
CHA2DS2-VASc Score Calculator — AFib Stroke Risk
Calculate CHA2DS2-VASc score for atrial fibrillation stroke risk. Checkbox-based scoring with annual stroke risk % and anticoagulation context.
Cholesterol Ratio Calculator (TC/HDL + LDL)
Calculate your total cholesterol/HDL ratio and estimate LDL with the Friedewald equation. See risk categories against AHA and CDC reference ranges.
Kidney Function Calculator — BUN/Cr, FENa, Osmolality
Calculate BUN/creatinine ratio, FENa (fractional excretion of sodium), and calculated serum osmolality with osmolar gap — clinical AKI interpretation aids.
Vertex Distance Calculator — Glasses to Contact Lens Power
Convert glasses power to contact lens power (or back) using the vertex distance formula, plus the ±4.00 D clinical significance threshold.
PT Assessment Calculator — Balance, Mobility & ARDS Tools
Berg Balance Scale, Elderly Mobility Scale, tidal volume (Devine/ARDSNet), and PF ratio (Berlin ARDS) calculators for PT and allied health assessment scoring.
Free Water Deficit Calculator — Hypernatremia Correction
Calculate free water deficit for hypernatremia from body weight, age/sex TBW fraction, and serum sodium. Includes the 0.5 mEq/L/hour safe correction limit.
Prostate Volume Calculator — Ellipsoid Method & PSA Density
Calculate prostate volume from length, width, and height using the ellipsoid formula, plus PSA density (PSAD) with the 0.15 and 0.20 thresholds.
Baby Percentile Calculator — Weight & Height for Age
Find your child's WHO/CDC growth percentile for weight-for-age or height/length-for-age using the official LMS method. Boys and girls, 0-20 years.
Blood Alcohol Level Calculator (BAC Estimator)
Estimate blood alcohol content from drinks, weight, and time using the Widmark equation. Educational only — never use to decide if it's safe to drive.
Keto Calculator — Macros, Calories & Net Carbs
Calculate your daily keto macros — fat, protein, and carb grams — from your BMR, TDEE, and goal, plus a net carbs helper for reading food labels.
A1C Calculator — A1C to Average Glucose (eAG) Converter
Convert A1C to estimated average glucose (eAG) in mg/dL or mmol/L, or IFCC mmol/mol. Bidirectional conversion with ADA normal/prediabetes/diabetes ranges.
BSA Calculator — Body Surface Area (Mosteller, DuBois, Haycock)
Calculate body surface area using Mosteller, DuBois, and Haycock formulas side by side. Includes an optional mg/m² dosing reference field.
Chronological Age Calculator for Testing & Assessments
Calculate exact chronological age in years, months, and days for WISC-V, WAIS-IV, and KTEA testing. Includes Pearson rounding and corrected age for preemies.
Corrected Calcium Calculator (Payne Formula)
Calculate albumin-corrected serum calcium using the Payne formula. mg/dL and mmol/L supported, with hypocalcemia/hypercalcemia severity tiers.
Fasting Calculator — Fasting Window & Stage Tracker
Calculate your intermittent fasting window for 16:8, 18:6, 20:4, OMAD, or custom protocols, with a live stage tracker showing ketosis and autophagy timing.
Fib-4 Calculator — Liver Fibrosis Risk Score
Calculate the FIB-4 index from age, AST, ALT, and platelet count. Includes the age-adjusted low-risk cutoff for patients 65 and older.
Half Birthday Calculator — Find Your 1/2 Birthday
Find your half birthday using the calendar (+6 months) or day-count (+182/183 days) method, with the exact date and countdown to the next one.
HOMA-IR Calculator — Insulin Resistance Score
Calculate HOMA-IR from fasting glucose and fasting insulin, in mg/dL or mmol/L. See where your score falls vs optimal, normal, and insulin-resistant ranges.
Invisalign Cost Calculator: 2026 Prices by Complexity & Insurance
Estimate Invisalign treatment cost by complexity, insurance, location, and provider type. Shows after-insurance cost and monthly payment breakdown.
NASCET Calculator: Carotid Artery Stenosis Percentage
NASCET carotid stenosis calculator. Enter stenosis and distal ICA diameters to get NASCET %, severity category, ECST equivalent, and CEA treatment thresholds.
Prescription Refill Date Calculator: When Can I Refill My Medication?
Calculate when you can refill a prescription based on fill date, days supply, and insurance policy. Track multiple medications with status alerts.