Free Fitness Calculators
33 evidence-based calculators for body composition, nutrition, strength, cardio, and power. No sign-up required.
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Know your body
BMI, body fat %, ideal weight — the foundational metrics for tracking physical change.
BMI Calculator
Calculate your Body Mass Index and see which WHO weight category you fall into.
BMI is a screening tool, not a diagnostic measure of body fat or health. It cannot distinguish muscle from fat — a muscular athlete may be classified 'overweight.' For a true body composition breakdown, a DEXA scan is available at most sports medicine clinics.
Body Fat % Calculator
Estimates body fat percentage without calipers or a lab.
Navy method accuracy: ±3–4%. For best results, measure at the same time each day.
Ideal Body Weight
Returns a healthy weight range for your height using Devine, Robinson, and Miller formulas averaged.
Average across three formulas
Ideal weight varies with muscle mass, bone density, and frame size. Use as a general reference. These formulas were developed for clinical populations — an athlete may healthily exceed this range.
Waist-to-Hip Ratio
Divides waist by hip circumference to assess abdominal fat distribution and cardiovascular risk.
WHO classification: Low = low risk, Moderate = intermediate, High = substantially increased risk. For a more complete cardiometabolic risk picture, combine with blood pressure, fasting glucose, and a lipid panel — available via your GP.
Lean Body Mass
Calculates the weight of everything except fat — muscle, bone, organs, and water — using Boer's formula.
Lean body mass
Boer's formula is well-validated for athletic populations. Results may differ ±2–3 kg from a DEXA scan. For exact lean mass by body segment (arms, legs, trunk), request a DEXA scan at a sports science or imaging clinic.
FFMI Calculator
Fat-Free Mass Index — measures how much muscle mass you carry relative to your height. The bodybuilder's alternative to BMI.
Use the Body Fat % calculator if unsure.
Normalized FFMI adjusts for height. Research by Kouri et al. (1995) found that pre-steroid era champions averaged ~25 normalized FFMI, suggesting ~25–26 is the natural upper limit for men. These are statistical population bounds — individual genetics may allow slightly higher values naturally.
Waist-to-Height Ratio Calculator
Research suggests keeping your waist circumference below half your height. This ratio is a stronger cardiovascular risk predictor than BMI alone.
Measure at the narrowest point, usually just above the navel.
A 2010 meta-analysis of over 300,000 participants found WHtR was a better predictor of cardiovascular events than BMI or waist circumference alone. The "keep your waist below half your height" rule is endorsed by the International Obesity Task Force as a simple universal threshold.
Fuel your performance
TDEE, calorie targets, macros, protein, hydration, fasting schedules, and weight-loss planning.
TDEE Calculator
Total Daily Energy Expenditure — how many calories your body burns per day.
Use the Body Fat % calculator to find this, or enter manually.
Total Daily Energy Expenditure
Uses Mifflin-St Jeor (1990), the most accurate BMR equation for most people.
Calorie Target Calculator
Takes your TDEE and a body-composition goal to output a daily calorie target with the right surplus or deficit.
Use the TDEE Calculator above, or enter manually.
0.5 kg ≈ 3,500 kcal. A 500 kcal/day deficit creates roughly 0.5 kg loss per week. Track your actual weight weekly for 4 weeks and adjust intake by ±100–200 kcal based on the trend — real-world tracking beats any formula.
Macro Calculator
Splits your daily calorie target into grams of protein, carbohydrates, and fat based on your preferred diet style.
Protein & carbs = 4 kcal/g · Fat = 9 kcal/g. Adjust to food preferences and performance. A registered sports dietitian can fine-tune macros based on bloodwork and performance goals.
Protein Intake Calculator
Recommends daily protein based on bodyweight and training goal, referencing ISSN guidelines (1.6–2.2 g/kg for active people).
Source: ISSN Position Stand on Protein and Exercise (Stokes et al., 2018). Population-level ranges — individual needs vary with training age, gut absorption, and recovery demands.
Water Intake Calculator
Estimates daily hydration needs from bodyweight and activity level using a 35 ml/kg baseline with exercise adjustment.
Includes water from all beverages. Coffee and tea count toward your total. Add ~0.5 L for every kg lost during a workout. Urine color (pale yellow) is the most practical daily hydration indicator — more reliable than any formula.
Intermittent Fasting Calculator
Set your eating window start time and IF protocol. Get your eating window, fasting window, and suggested break-fast time.
Black coffee, plain tea, and water do not break a fast. Electrolytes without calories are generally fine. Avoid intense training in the first week of a new protocol. The research on IF shows benefits mainly from calorie reduction — not the fasting itself — so hit your nutrition targets within your eating window.
Weight Loss Pace Calculator
Given your current weight, target weight, and daily calorie deficit, estimates how long it will take to reach your goal.
Deficit = calories eaten below your TDEE. A 500 kcal deficit = ~0.5 kg/week.
One kg of fat ≈ 7,700 kcal. The 3,500 kcal/lb rule is a simplification — metabolic adaptation means rate slows as you lose weight. A safe, sustainable rate is 0.5–1% of body weight per week. Deficits above 1,000 kcal/day risk muscle loss without adequate protein and resistance training.
Train smarter
1RM, training load percentages, Wilks score, RPE, strength levels, volume tracking, and progressive overload planning.
One Rep Max (1RM) Calculator
Estimates your maximum lift from a submaximal set using Epley, Brzycki, and Lombardi formulas — with guidance on which is most reliable for your rep range.
Average estimated 1RM
Formula accuracy decreases with higher reps. For an exact 1RM, perform a max-effort single after a proper warm-up (build to ~90%, then attempt 95% and 100% in 2–3 attempts) with a spotter.
Rep Max % Converter
Enter your 1RM to get a full intensity table showing estimated weight and rep range for each percentage zone.
Use the 1RM Calculator above, or enter manually.
These percentages are only as accurate as the 1RM entered. Individual rep capacity at a given % varies — some lifters consistently exceed the table at moderate percentages.
Wilks Score Calculator
Compares powerlifting totals across bodyweights and sexes. Supports Wilks, Dots, and IPF GL Points — the three industry-standard formulas.
Squat + Bench Press + Deadlift
Wilks score >400 is considered competitive. Elite lifters score 500+. Formula by Robert Wilks (1998). For competition use, ensure lifts are performed on a calibrated platform under federation standards — gym PRs may not account for depth or equipment variation.
Training Volume Calculator
Computes weekly training volume (sets × reps × weight) per muscle group to identify under- or over-trained areas.
Volume by Muscle Group
Recommended weekly volume: 10–20 sets per muscle group for hypertrophy (Israetel, 2019). Your personal maximum recoverable volume (MRV) depends on sleep quality, nutrition, and training age — start at the lower end and add 1–2 sets per week to find your limit.
Progressive Overload Planner
Generates a week-by-week progression table from a starting weight, applying a chosen % increase each week.
Weekly Progression
Round to the nearest available plate (e.g. 2.5 kg increments). Deload every 4–6 weeks as needed. Linear progression is most effective for beginners (0–2 years training). Intermediate lifters typically need wave loading or periodisation to continue progressing.
Strength Level Calculator
Compares your lift to population strength standards — from untrained to elite — based on bodyweight and sex.
Strength standards are based on sex, bodyweight ratio, and population lifting data. These represent approximate milestones — genetics, training age, and equipment (belt, wraps) affect individual limits. Use these as motivation markers, not hard limits.
RPE Calculator
Converts between RPE (Rate of Perceived Exertion) and % 1RM. Find your working weight for any RPE target, or estimate your 1RM from a rated set.
RPE is subjective — calibrate it over time. A true RPE 10 means technical failure, not just discomfort. RPE 8 (2 reps in reserve) is the most common training zone for hypertrophy and strength. Avoid RPE 10 on main lifts unless peaking for competition.
Push your limits
VO₂ max, heart rate zones, target HR, running pace, race prediction, FTP, and calories burned.
VO2 Max Estimator
Estimates VO₂ max from field tests or resting heart rate, with ACSM age/sex classifications and personal training zones.
Run 1.5 miles (2.41 km) at maximum effort and record finish time.
Run as far as possible in 12 minutes on a flat surface or running track.
Measure first thing in the morning before getting out of bed. Average over 3 mornings for best accuracy.
Enter total minutes for the distance (e.g. 270 min for a 4:30 marathon). Use a recent race or time trial — not a GPS estimate.
Field tests estimate VO₂ max with ±5–10% accuracy. For a precise measurement, a maximal incremental test (treadmill or cycle ergometer with metabolic cart) is available at sports physiology labs and cardiac rehab centres.
Heart Rate Zone Calculator
Computes 5 training heart rate zones with purpose and BPM range for each.
Zone 2 (aerobic base) is where most endurance athletes spend 80% of training time. Zone 4–5 are reserved for intervals. Formula-based zones carry ±10–12 bpm uncertainty. For precise zone boundaries, a lactate threshold test (graded blood lactate sampling) accurately defines your Zone 4/5 transition.
Target Heart Rate Calculator
Uses the Karvonen formula to calculate a personalized target HR range for any workout intensity.
Karvonen formula: THR = ((MaxHR − RestingHR) × intensity%) + RestingHR. More accurate than simple %MaxHR because it accounts for your fitness level. For personalised zone boundaries, a lactate threshold test at a sports lab directly measures the HR at which lactate accumulates — the most accurate available method.
Running Pace Calculator
Convert between pace, speed, and total race time. Also shows estimated finish times for all major race distances.
Running pace
Race finish times at this pace
Pace calculations are exact for the entered time/distance. For race-day accuracy, account for elevation, heat, and taper — a GPS watch with live pace feedback is the most practical tool.
Calories Burned Calculator
Estimates calories burned during exercise using MET (Metabolic Equivalent of Task) values for common activities.
Formula: MET × weight(kg) × time(hours). Individual variation is ±15–20%. Source: Ainsworth et al. Compendium of Physical Activities. For a precise measurement, indirect calorimetry (portable metabolic analyser or lab metabolic cart) is available at sports science facilities.
Race Time Predictor
Predicts your finish time for any race distance based on a known result. Uses the Riegel formula — the most widely validated endurance performance model.
Riegel formula: T₂ = T₁ × (D₂ / D₁)^1.06. The 1.06 exponent accounts for the fatigue factor — running gets disproportionately harder at longer distances. Accuracy degrades for very short distances (<3 km) or ultra-long events (>50 km). Training and race-day conditions significantly influence actual results.
Cycling FTP Calculator
Estimates your Functional Threshold Power — the highest average power you can sustain for one hour — from a short effort test.
FTP is the cornerstone of cycling training. Re-test every 6–8 weeks to track progress. Your zones shift as FTP improves. A power meter or smart trainer is required for accurate testing — using heart rate as a proxy for power introduces significant error.
Unleash your power
Vertical jump power, sprint speed, power-to-weight ratio, reactive strength, and plyometric volume.
Vertical Jump Power Calculator
Estimates peak lower-body power from your vertical jump height using Lewis, Sayer, and Harman formulas.
Sayer and Harman equations (1991–1999) are more accurate for trained athletes; the original Lewis formula tends to underestimate peak power. For a lab-grade measurement, a force plate countermovement jump test is the gold standard.
Sprint Speed Calculator
Calculates your sprint speed from distance and time — outputs m/s, km/h, mph, and an athletic speed classification.
Average sprint speed peaks in the first 30–60m before fatigue sets in. Bolt's average 100m speed was 10.44 m/s (37.6 km/h); his peak instantaneous speed reached ~12.4 m/s. Elite team-sport athletes typically reach 8–9 m/s. GPS vests or timing gates provide the most accurate sprint timing.
Power-to-Weight Ratio Calculator
Divides your power output by body weight to give W/kg — the universal measure of athletic work capacity.
From a cycling test, rowing ergometer, or power meter reading.
W/kg is most commonly used in cycling (FTP/kg), but applies to rowing, sprinting, and weightlifting. Tour de France climbers sustain ~6–6.5 W/kg for 30+ minutes. Untrained adults average 1.5–2.5 W/kg. Values above 5.5 W/kg are typically only seen in elite endurance athletes.
Reactive Strength Index (RSI) Calculator
RSI measures your stretch-shortening cycle efficiency — how fast you absorb a landing force and redirect it into a powerful takeoff. A key metric for plyometric programming, sprint development, and tracking reactive strength gains over time.
Measured from a drop jump or repeat jumping test.
Time from landing to takeoff in milliseconds.
Time airborne from takeoff to landing. Apps like My Jump 2 and PUSH Band output this directly.
Time from landing to takeoff in milliseconds.
RSI = jump height (m) ÷ ground contact time (s). A higher value means faster, more explosive ground contacts. For reliable measurement use a contact mat or force plate — smartphone apps like My Jump 2 can estimate jump height from video within ~10%. Track RSI across an 8-week plyometric block; a gain of 0.2–0.4 is a meaningful training adaptation.
Plyometric Volume Calculator
Tracks total foot contacts per session and flags safe training volume based on NSCA plyometric programming guidelines.
NSCA recommends tracking foot contacts (each foot landing = 1 contact) and limiting session volume based on training level. Higher-intensity jumps like depth jumps carry 4–8× the joint loading of low-intensity jumps. Reduce volume by 30–50% when introducing any new high-intensity exercise.
Body Composition
Nutrition & Metabolism
Strength & Performance
Cardio & Endurance
Power & Explosiveness
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