Numbers don't lie.
The Math Behind
Weight Loss
Calculate your BMI, figure out your macros, and understand the thermodynamics of calories in vs. calories out. Three tools, zero guesswork.
How to use this hub
Weight loss math is not a personality test. It is three jobs in order: know a rough size of the problem (BMI), estimate how much energy you burn and how to split protein/fat/carbs (macros / TDEE), then lock the only law that moves the scale (CICO).
Start with CICO if you already know you are overeating and want the evidence spine. Start with macros if you want targets for a tracker app this week. Use BMI as a coarse map — useful for population context, incomplete for athletes and edge body compositions.
- Stakes: without a calorie target you are negotiating with vibes.
- Next: after numbers, buy food that makes the deficit survivable — Grocery Guide.
- Honesty check: if the calculator scares you, that is data, not a moral verdict.
General information only — not medical advice. If you have a clinical condition, talk to a clinician before aggressive deficits.
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BMI Calculator & Guide
Calculate your Body Mass Index, explore the full reference table by height and weight, and understand what BMI tells you — and where it falls short.
Calculate your BMI →
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Macros Calculator
Calculate your TDEE using the Mifflin-St Jeor equation and get personalized macronutrient targets for fat loss, maintenance, or muscle gain.
Calculate your macros →
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CICO Science
The definitive evidence for why energy balance determines weight. Five common objections, answered with peer-reviewed research.
Read the science →
Know what to buy?
Put the numbers into practice with our grocery guide — high protein, high volume, low sugar.
Grocery Guide →