What is a healthy BMI?

A healthy BMI is between 18.5 and 24.9. Underweight is below 18.5, overweight is 25–29.9, and obese is 30 or above.

How many calories should I eat to lose weight?

A safe calorie deficit is 500–750 calories per day. Calculate your TDEE first, then subtract your deficit.

What are macros and how do I calculate them?

Macros are protein, carbohydrates, and fats. A standard split is 30% protein, 40% carbs, 30% fat.

How much protein do I need per day?

For muscle building, aim for 1.6–2.2g of protein per kg of bodyweight.

How do I calculate my daily calorie needs?

Daily calorie needs = BMR × activity factor. BMR is calculated from age, sex, weight, and height using the Mifflin-St Jeor equation.

💪 Fitness Tools

Free Fitness Calculators — BMI, Calories, Macros & More

Calculate your BMI, daily calories, macro split, protein needs, body fat percentage, one rep max, heart rate zones, and more. 11 science-based calculators — free, instant, no signup.

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Fitness Tools

All Fitness Calculators

11 tools

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BMI Calculator

Calculate your Body Mass Index and understand what the number means.

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Calorie Calculator

Calculate your TDEE — total daily energy expenditure — to hit your goals.

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Calorie Deficit Calculator

Find the right calorie deficit to lose weight safely without muscle loss.

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Macro Calculator

Get your ideal protein, carb, and fat targets for any fitness goal.

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Protein Calculator

Calculate daily protein intake based on your weight, goals, and activity.

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One Rep Max Calculator

Estimate your 1RM for any lift using multiple proven formulas.

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Body Fat Calculator

Estimate body fat percentage using the US Navy measurement method.

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Heart Rate Calculator

Find your max heart rate and ideal training zones for fat burn and cardio.

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Running Pace Calculator

Convert between pace, speed, and finish time for any race distance.

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Ideal Weight Calculator

Find your healthy weight range based on height using four medical formulas.

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Workout Volume Calculator

Track total training volume (sets × reps × weight) for progressive overload.

Quick Fitness Reference

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18.5–24.9

Healthy BMI range (WHO)

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500 kcal

Safe daily deficit for fat loss

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1.6–2.2g/kg

Protein for muscle building

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220 – age

Max heart rate formula (BPM)

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0.033L/kg

Daily water intake baseline

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70–80%

Ideal body fat reduction zone

Free Fitness Calculators for Weight Loss

Losing weight requires a calorie deficit — burning more than you consume. Our fitness calculators give you every number you need: your TDEE (total daily energy expenditure) tells you how many calories you burn at your current activity level, the calorie deficit calculator tells you how large a deficit to create for your target rate of loss, and the macro calculator splits that calorie target into protein, carbohydrates, and fat based on your goals. Together, these three calculators replace a dietitian's first consultation.

Free Fitness Calculators for Building Muscle

Building muscle requires a calorie surplus paired with adequate protein. Use the protein calculator to find your daily protein target (typically 1.6–2.2g per kg of bodyweight for muscle gain), the one rep max calculator to structure your progressive overload, and the workout volume calculator to optimise your weekly training sets per muscle group. The body fat calculator gives you a baseline so you can track body composition changes rather than relying solely on the scales.

BMI Calculator — Is BMI Still Useful in 2025?

BMI (Body Mass Index) is widely criticised for ignoring muscle mass, bone density, and fat distribution — a muscular athlete and a sedentary person of the same height and weight get the same BMI score. Despite its limitations, BMI remains a useful first-pass population health screening tool. For a more complete picture, pair your BMI with a body fat percentage measurement. Our body fat calculator uses the Navy method (neck, waist, and hip measurements) which is more accurate than BMI for assessing body composition.

Frequently Asked Questions

A healthy BMI is 18.5–24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese. BMI doesn't distinguish fat from muscle — athletes often show high BMI with low body fat. Pair it with a body fat calculator for accuracy.

Calculate your TDEE first with our Calorie Calculator, then subtract 500–750 kcal/day for safe fat loss (0.5–0.75 kg/week). Never go below 1,200 kcal (women) or 1,500 kcal (men) without medical supervision.

Macros are protein, carbohydrates, and fat. A common split for fat loss is 40% protein / 30% carbs / 30% fat. For muscle gain: 30% protein / 50% carbs / 20% fat. Use our Macro Calculator for a personalised breakdown.

For muscle building: 1.6–2.2g per kg of bodyweight (0.7–1g/lb). For maintenance: 0.8g/kg. Spread intake across 3–5 meals for optimal muscle protein synthesis. Our Protein Calculator gives your exact daily target.

The most accurate formula is Epley: 1RM = weight × (1 + reps/30). Perform 3–5 reps at a challenging weight and plug the numbers into our One Rep Max Calculator. Never attempt a true 1RM without a spotter.

Calorie needs = BMR × activity multiplier. BMR uses the Mifflin-St Jeor equation (age, sex, height, weight). Sedentary × 1.2; moderately active × 1.55; very active × 1.725. Our Calorie Calculator shows targets for loss, maintenance, and gain.

To lose 1 kg per week, you need a 1,000-calorie daily deficit below your TDEE — though this rate risks muscle loss and is difficult to sustain. Most professionals recommend a 500-calorie deficit (0.5 kg/week) for steady fat loss. Use our Calorie Deficit Calculator.

The standard healthy BMI range (18.5–24.9) applies to both men and women. However, women naturally carry a higher percentage of body fat than men at the same BMI. Some researchers argue the healthy range for women extends to 25–27 without increased health risk, particularly for women over 60.

Start with your calorie target (TDEE minus deficit). Allocate protein first at 1.6–2g/kg (critical for preserving muscle), fat at a minimum of 0.8g/kg (hormonal health), then fill remaining calories with carbohydrates. Use our Macro Calculator for your personalised split.