calculate Four calculators, all running in your browser

Health tools that show their working

Enter your numbers, get a result with its formula, its assumptions and its limits. Nothing is saved, sent or shared.

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scale BMI local_fire_department Calories water_drop Hydration bedtime Sleep cycles
scale

Body mass index

Weight relative to height, using CDC adult BMI categories.

info BMI does not distinguish muscle from fat and is not valid during pregnancy, for children, or for highly trained athletes. Treat it as one rough screening number among several.

monitor_weight

No result yet

Enter your height and weight, then calculate to see your BMI and healthy weight range.

local_fire_department

Daily calorie needs

Mifflin–St Jeor resting metabolic rate, scaled by activity and goal.

info These are population estimates and can differ from your real needs by 10–15%. Do not use them to drop below roughly 1,200 kcal a day without supervision from a doctor or registered dietitian.

restaurant

No result yet

Fill in your details to see your resting rate, daily expenditure and a macronutrient split.

water_drop

Daily hydration target

Body weight, training minutes, and climate, converted into fluid ounces.

0 min90 min3 hours

info Food contributes roughly 20% of daily fluid. If you take diuretics or have heart or kidney disease, your fluid allowance may be deliberately restricted — follow your doctor's figure, not this one.

local_drink

No result yet

Add your weight and today's activity to get a litre target and a simple drinking schedule.

bedtime

Sleep cycle timing

Times built on 90-minute cycles, including how long you take to fall asleep.

info Cycle length averages 90 minutes but varies between people and across a night. Use these times as a guide. Loud snoring, gasping in sleep or persistent daytime sleepiness should be assessed by a doctor.

nights_stay

No times yet

Pick a wake time or bedtime to see four options that finish at the end of a cycle.

Where these estimates stop working

Every formula here was derived from population averages of healthy adults. That makes them useful starting points and poor final answers. Treat a result as a hypothesis to test over a month, not a rule to obey today.

  • pregnant_woman Pregnancy and breastfeeding change all four targets.
  • child_care Children and teenagers need age-specific charts.
  • fitness_center High muscle mass inflates BMI without added risk.
  • medical_information Kidney, heart and thyroid conditions override these numbers.

A result you cannot place?

Send us the number and what you were hoping to change. We will explain what it does and does not mean and point you to the guides worth reading — or tell you plainly when it is a question for your doctor.

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