Fitness Tools
Fitness calculators, built right.
Accurate, free fitness calculators to track calories burned, find your ideal weight, and hit your fitness goals. No signup, no ads, instant results.
Fitness Tools
Free fitness calculators.
11 entries
Rucking Calorie Calculator
Calculate exactly how many calories you burn rucking based on your body weight, pack weight, distance, and pace. Uses the Pandolf load-carriage equation.
↗ Mifflin-St Jeor 02TDEE Calculator
Calculate your Total Daily Energy Expenditure with the Mifflin-St Jeor equation, plus maintenance, cutting, and bulking calorie targets.
↗ Epley · Brzycki · Lander 03One-Rep Max Calculator
Estimate your true 1RM from any submaximal set using the Epley, Brzycki, and Lander formulas — with a full training percentage chart.
↗ U.S. Navy method 04Body Fat Calculator
Estimate your body fat percentage, fat mass, and lean mass with the U.S. Navy circumference method — just a tape measure needed.
↗ Body-weight method 05Water Intake Calculator
Get your personalized daily water target based on body weight, exercise volume, and climate — in ounces, liters, and cups.
↗ WHO categories 06BMI Calculator
Calculate your Body Mass Index in metric or imperial units. Shows your WHO category, healthy weight range, and BMI Prime ratio.
↗ WHO category table 07BMI Chart by Height & Weight
Reference chart showing the healthy, overweight and obese weight range for every height — in pounds and kilograms, with a highlight-your-row tool.
↗ 5 clinical formulas 08Ideal Weight Calculator
See your ideal body weight from five clinical formulas — Devine, Hamwi, Robinson, Miller and Broca — with a consensus range and your Ponderal Index.
↗ Thomas et al. (2013) 09Body Roundness Index
A research-backed alternative to BMI using your waist and height. Captures central body fat — the kind tied to health risk — that BMI misses entirely.
↗ Jackson-Pollock · Siri 10Siri Body Fat Calculator
Estimate body fat percentage from skinfold calipers using the Jackson-Pollock and Siri equations — or convert a body density value directly.
↗ BMI formula, inverted 11Reverse BMI Calculator
Enter your height and a target BMI to instantly find the exact weight you need to reach your goal. Includes a visual BMI range indicator.
↗Why Use These Fitness Calculators?
Most online fitness calculators are cluttered with ads, require you to create an account, or give generic results that don't account for your specific situation. Every calculator on ForgeYourFit is built to be fast, accurate, and genuinely useful — no fluff, no signup, no cost.
How Accurate Are These Calculators?
All calculators on this site use scientifically validated formulas and data sources. The rucking calorie calculator uses the Pandolf load-carriage equation from U.S. Army research (Pandolf, Givoni and Goldman, 1977). The reverse BMI calculator uses the standard WHO BMI formula. Results are estimates — individual variation, terrain, and fitness level can affect actual outcomes by 10 to 15 percent.
More Calculators Coming Soon
- TDEE Calculator — Total Daily Energy Expenditure based on activity level
- Body Fat Percentage Calculator — using measurement-based methods
- Macro Calculator for Weight Loss — personalized protein, carb, and fat targets
- Running Calorie Calculator — pace, distance, and terrain-adjusted
From the Blog
Read the research behind the numbers.
Guides & breakdowns 8 articles