Weight Loss Mathematics — How to Calculate a Sustainable Deficit

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Overview

Weight loss is fundamentally a numbers game, but getting the numbers right prevents muscle loss, metabolic slowdown, and the frustrating weight loss plateaus most people experience.

The Formula

Weekly loss = (Daily deficit × 7) ÷ 7,700 (calories per kg of fat)

Standard formula used by professionals worldwide

Worked Example

Step-by-step

500 cal/day deficit × 7 = 3,500 calories/week ÷ 7,700 = 0.45kg loss per week

Key Points

Accuracy: Results are as accurate as the inputs you provide
Units: Always use consistent units throughout your calculation
Privacy: All calculations on CalcHub Pro run in your browser — nothing is sent to any server

Frequently Asked Questions

Why does weight loss slow over time?

Metabolic adaptation. As you lose weight TDEE decreases. Recalculate every 4-6 weeks.

Can I lose faster with a bigger deficit?

Large deficits cause muscle loss, nutrient deficiencies, and metabolic slowdown — counterproductive.

Do I need to count every calorie?

Not forever, but counting for 2-4 weeks builds accurate awareness of portion sizes.

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