FitCalcs

Turn an estimate into a useful plan

A calculator result is a starting point, not a prescription. FitCalcs shows the equation, assumptions, and source behind each result so you can understand what the number means and adjust it using your own data. Your entries are calculated in your browser; no account is required and your height, weight, age, and measurements are not submitted to us.

For calorie planning, start with a TDEE estimate, choose a modest goal adjustment with the calorie deficit calculator, then use the macro calculator to divide that target into protein, carbohydrate, and fat. Track your average body weight for two to three weeks before changing the target: activity multipliers and metabolism equations cannot measure your actual daily movement.

A worked example

Suppose a calculator estimates maintenance at 2,400 kcal per day. A 400-kcal deficit gives a starting target of 2,000 kcal. If the three-week weight trend is flat and food tracking is consistent, the estimate was probably high; reducing the target by 100–200 kcal is more informative than making a drastic cut. If weight is falling faster than intended or training suffers, add calories back. This feedback loop is more useful than treating any single calculated result as exact.

Transparent methods, including the limits

We use published equations such as Mifflin–St Jeor for resting energy, the U.S. Navy circumference method for body-fat estimates, and Epley, Brzycki, Lombardi, and Lander for one-rep-max estimates. Where the evidence is uncertain—such as whether gradually increasing calories after a diet prevents weight regain—we say so. Our methodology documents the formulas, sources, and limitations, while the editorial policy explains how pages are reviewed and corrected.

Want more context before using a tool? Our guides explain the concepts in plain English with worked examples and source links, and our reference charts publish the same calculations as tables you can read a number off directly. Our research pages go further and test the formulas against each other, including where that reflects badly on a tool here. These tools are intended for general education by healthy adults, not diagnosis or individualized medical care.