"Drink more water." "Eat fewer calories." "Lose some weight." These are all reasonable instructions and almost completely useless. A number is what turns advice into action. CalcMaster's health section is a small but high-utility set of tools that give you the number, explain the formula, and stop short of telling you what to do with it (that's your doctor's job).
Body composition
BMI
The most-searched health metric in the world — and also the most misunderstood. BMI = weight (kg) / height (m)². It's useful as a population statistic and a rough flag for the average adult, but it doesn't know anything about muscle, frame, or where fat is stored. An athlete with 10% body fat can have a "overweight" BMI. Use it as a starting point, never as a verdict.
Body Fat %
The US Navy method — circumferences only, no calipers. Less accurate than DEXA but free and fast. Better than BMI for most people because it actually measures composition, not just weight.
Ideal Weight
Calculates the Devine / Hamwi / Miller formulas side-by-side. Spoiler: they all give different numbers and none of them is the answer.
Energy & calories
| Calculator | What it tells you |
|---|---|
| BMR | Calories burned at complete rest (Mifflin-St Jeor) |
| Calorie Needs | TDEE — BMR × activity multiplier |
| Macro Splitter | Split your daily calories into protein / carbs / fats |
The path is: BMR → TDEE → adjust for goal (cut / maintain / bulk) → split into macros. The calculators chain together so you can run the whole flow in under a minute.
Day-to-day
- Water Intake — daily hydration target based on weight + activity
- Pregnancy Due Date — EDD from LMP, plus current trimester and week
The honest disclaimer
None of these tools replace a doctor, a nutritionist, or a coach. They take published, peer-reviewed formulas and let you plug in numbers. They don't know your bloodwork, your history, your goals, or your medications. Use them as a starting point for the right conversation — not as a substitute for it.
Browse the health category for the full list.
