CALCULATOR

Goal Body Fat Calculator

What you will weigh at your target body fat percentage, assuming you keep your lean mass, and how long it should take.

Goal weight

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Target weight–

Fat to lose–

Your lean body mass–

Current fat mass–

Fat mass at target–

Estimated time–

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Working out your goal weight from body fat

Setting a goal weight from a number on the scale is guesswork. Setting it from a target body fat percentage is arithmetic, provided you know your current body fat and assume your lean mass stays constant.

The logic is simple. Your lean body mass is the part you want to keep. At any target body fat percentage, your weight is lean mass divided by one minus that percentage. Everything above that figure is fat you would be losing.

The assumption doing the work here is that lean mass holds. That is achievable, but it is not automatic. It requires protein at the upper end of the range and resistance training throughout the deficit. Without both, some of the loss comes from muscle and your actual goal weight ends up lower and leaner-looking than the calculation suggests.

Frequently asked questions

How do I calculate goal weight from body fat percentage?

Lean mass divided by one minus the target body fat as a decimal. At 64 kg lean mass and a 15 percent target, goal weight is 64 / 0.85, or about 75 kg.

Is my target body fat realistic?

For men, 10 to 15 percent is lean and sustainable for most; below 8 percent is competition territory. For women, 18 to 25 percent is the equivalent range, and very low levels can disrupt menstrual function.

Why is my goal weight higher than expected?

Because you carry more lean mass than you assumed. That is a good position, not a problem.

How long will it take?

At 0.5 kg per week, divide the fat to lose by 0.5. Slower rates protect muscle better, particularly as you get leaner.

Sources

Gallagher D et al. Healthy percentage body fat ranges. American Journal of Clinical Nutrition, 2000.
Helms ER et al. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes. IJSNEM, 2014.
National Institutes of Health, Office of Dietary Supplements. Nutrient fact sheets. ods.od.nih.gov
NHS. Nutrition and health guidance. nhs.uk
US Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans, 2025-2030. dietaryguidelines.gov

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General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.