Health Calculators

Which energy number you actually want

Three tools here answer three stacked questions. BMR is what your body uses at complete rest. TDEE multiplies that by an activity factor to estimate what you use in a normal day. The calorie deficit calculator then works backwards from TDEE to an intake for a target rate of change. If you are trying to plan eating, TDEE is almost always the starting point rather than BMR, and BMI answers a different question entirely: it is a ratio of weight to height and says nothing about body composition.

TDEE Calculator

for daily energy expenditure, the number most eating plans are actually built from.

BMR Calculator

for resting energy alone, before any activity is added.

BMI Calculator

for the weight-to-height ratio, with the WHO bands drawn out and their limits stated.

Protein Intake Calculator

for published intake ranges by goal, each attributed to the document it comes from.

Calorie Deficit Calculator

for the intake implied by a target rate of loss, with the Wishnofsky rule and its problems explained.

Where these calculations go wrong

Reading BMI as a body-fat measurement

BMI divides weight by height squared and nothing else. It cannot distinguish muscle from fat, which is why a very muscular person can land in the overweight band while carrying little fat. The body fat calculator uses circumference measurements instead and answers the question BMI is often mistaken for.

Treating an activity multiplier as precise

The step from BMR to TDEE runs through a broad activity factor, and the honest range around the result is wide. Two people with identical inputs and genuinely different daily movement will get the same estimate, which is the limitation of the method rather than a fault in the calculation.

Questions about health

Should I use BMR or TDEE to plan what I eat?

TDEE, in almost every case. BMR describes what the body uses at rest, so eating to BMR ignores everything you do in a day. TDEE applies an activity multiplier to BMR and is the figure the calorie tools work back from.

Do these calculators give medical advice?

No. They apply published formulas to the numbers you enter and show the working. Each page states what its formula does not account for. A calculator cannot see your history, medication or blood work, and none of these pages is a substitute for a clinician who can.

Related sections

• Pets for the same energy arithmetic applied to dogs and cats, where the multipliers differ entirely.
• Unit Converters for the weight and length conversions these formulas need when your measurements are in mixed units.