Every health calculator on Numeros, grouped by what you are trying to work out. All free, no sign-up, and each one shows the formula behind the number — because a health figure you cannot interpret is not much use.
Featured
- BMI Calculatorbody mass index with the category it falls in, plus the limitations that matter for athletes and older adults.
- BMR Calculatorbasal metabolic rate, what you burn at complete rest before any activity.
- Body Fat Calculatorbody fat percentage from circumference measurements, which tracks composition better than weight alone.
- Calorie Calculatordaily calories for maintenance, loss or gain, from your activity level and goal.
- Macro Calculatorprotein, carbohydrate and fat targets in grams for your calorie goal.
- TDEE Calculatortotal daily energy expenditure, the number every nutrition target is built on.
- Water Intake Calculatordaily fluid needs adjusted for body weight, activity and climate.
- Pregnancy Due Date Calculatorestimated due date, current week and trimester, from your last period or conception date.
- Blood Pressure Calculatorwhich category a reading falls in, and what the current guidelines classify as elevated.
- Heart Rate Calculatorresting rate interpretation and what the ranges indicate.
General body metrics
- Blood Alcohol Calculatorestimated BAC and hours to clear. An estimate only — never a basis for deciding to drive.
- Body Surface Area CalculatorBSA by the standard clinical formulas, used for dosing rather than fitness.
- FFMI Calculatorfat-free mass index — how much muscle you carry for your height, and where that sits against the reported natural ceiling.
- Ideal Weight Calculatorthe range four standard formulas produce, and why they disagree with each other.
- Lean Body Mass Calculatorthe weight that is not fat, useful for dosing, nutrition targets and tracking real progress.
- Waist-Hip Ratio Calculatora fat-distribution measure that predicts some risks better than BMI does.
- Waist-to-Height Ratio Calculatorthe simplest single screening ratio, with one threshold that works across heights.
Nutrition
- Caffeine Limit Calculatoryour daily ceiling and how long a dose stays active, using caffeine's half-life.
- Calories Burned Calculatorenergy used by activity, duration and body weight, using MET values.
- Fiber Intake Calculatorrecommended daily fibre by age and sex, and how far typical intake falls short.
- Protein Intake Calculatordaily protein by body weight and training load, with the evidence-based ranges.
Pregnancy & reproductive health
- Conception Date Calculatorthe likely conception window worked backward from a due date.
- Ovulation Calculatorthe fertile window across your cycle length.
- Period Calculatorprojected dates for coming cycles from your average length.
- Pregnancy Weight Gain Calculatorthe recommended range for your pre-pregnancy BMI and current week.
Vitals & laboratory values
- Blood Sugar Calculatorglucose interpretation, fasting and post-meal, with unit conversion.
- Cholesterol Calculatortotal, LDL, HDL and the ratios clinicians actually look at.
- Ferritin Calculatoriron stores interpretation, where the range differs from hemoglobin's.
- Hemoglobin Calculatorreference ranges by age and sex, and what low values commonly indicate.
- Kidney Function CalculatoreGFR from creatinine, with the CKD stage it corresponds to.
- Liver Enzyme CalculatorALT, AST and the ratio between them, which carries more information than either alone.
- QTc Calculatorcorrected QT interval by Bazett, Fridericia and Framingham, which give different answers.
- SpO2 Calculatorblood oxygen saturation ranges and when a reading warrants attention.
- Target Heart Rate Calculatortraining zones from your maximum and resting rates.
- Body Temperature Calculatorfever thresholds by measurement site, which differ more than most people expect.
- TSH Calculatorthyroid stimulating hormone ranges and what high or low suggests.
- Vitamin D Calculatorsufficiency thresholds and the intake typically needed to correct a deficiency.
- White Blood Cell CalculatorWBC count with differential, and what shifts in each cell type suggest.
Fitness & performance
- One Rep Max Calculatorestimated 1RM from a set at a lower weight, across several established formulas.
- Pace Calculatorpace, time and distance for running and walking, in either unit system.
How to read a health number properly
Every calculator here returns a figure, and a figure on its own can mislead in three predictable ways. Knowing them makes the tools far more useful:
| The trap | What to do instead |
|---|---|
| Treating a population average as a personal target | BMI, ideal weight and calorie formulas describe populations. A muscular person registers as overweight by BMI and is not. Use the number as a starting point and track your own trend |
| Reading a single measurement as a state | Blood pressure, heart rate and glucose all move through the day. One reading is a snapshot; three readings across a week are information |
| Assuming outside the range means something is wrong | Reference ranges are set so a percentage of healthy people fall outside them by design. A slightly abnormal result usually means repeat it, not panic |
The measurement worth tracking
If you only track one thing, make it a trend rather than a value. A single BMI reading tells you little; the same measurement monthly for a year tells you where you are heading, which is the part you can act on. The same applies to blood pressure, resting heart rate and weight — direction is more informative than position, and it is the one thing a clinician cannot reconstruct from a single visit.
These tools are built for that: fast enough to run repeatedly, with the formula visible so the numbers stay comparable across time.
Frequently asked questions
Are these calculators medically accurate?
The mathematics is exact and each tool uses a standard published formula, shown on the page. What they cannot do is account for you specifically — your medical history, medications, body composition or anything a clinician would observe. They are calculators, not assessments. Treat the output as a well-computed reference point, and take anything concerning to a doctor.
Why do different calculators give different ideal weights?
Because several formulas exist and they were derived from different populations for different purposes — Devine was built for drug dosing, not aesthetics. Our Ideal Weight Calculator shows all of them together precisely so the spread is visible. A range from four formulas is more honest than one number presented as the answer.
Is BMI actually useful?
For populations, yes — it correlates well with health outcomes across large groups, which is why it persists. For individuals it is cruder: it cannot distinguish muscle from fat, and misclassifies athletes and some older adults routinely. Body fat percentage and waist-to-height ratio describe an individual better. BMI is a reasonable first look, not a verdict.
Is my health data stored anywhere?
No. Every calculation runs in your own browser and nothing you enter is transmitted or saved. That matters more here than in most categories — weight, lab values and pregnancy dates are among the most sensitive things anyone types into a website. Nothing leaves your device, and closing the tab discards it.
My lab result is outside the reference range. What now?
Take it to the doctor who ordered it. Reference ranges are statistical boundaries, not diagnoses — they are set so that a small percentage of entirely healthy people fall outside them, and a mildly abnormal value often means the test should simply be repeated. Interpreting a result requires your history and the rest of the panel, which no calculator has.
Which calculator should I use to lose weight?
Start with TDEE to establish what you burn, then Calorie Calculator for a target with a sensible deficit, and Macro Calculator to split it. A word of caution: these produce estimates that can be several hundred calories off for an individual. Use the number as a starting point, then adjust based on what actually happens over three or four weeks.
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