Calculators for lifters and runners, with the formula shown.
Which fitness number to trust: calculators, formulas and device comparisons, checked against the validation studies behind them. 57 calculators for strength, running, body composition and recovery. Each one names the formula it uses, the study it comes from and where it stops being accurate.
= 68.0 ÷ 1.78² + 6.3 × (1.8 − 1.78)
21.6Above average — consistent training
What is AI Fit Hub?
A free set of fitness calculators for lifters and runners: FFMI, DOTS, one-rep max, VO2 max, Zone 2, race-time prediction and recovery. Each runs a named, published formula, so the same inputs always give the same answer, and each page says which study the formula comes from and where it stops being accurate. Nothing you enter leaves your browser.
Start with a goal
- Body Composition
BMI, body fat, lean mass, FFMI, and waist-to-hip metrics organized under one topical hub.
- Weight Loss
TDEE, calorie deficits, macro targets, fasting context, and practical fat-loss execution.
- Strength & Muscle
One-rep max, overload planning, training volume, protein, and powerlifting benchmarks.
- Nutrition
Protein, macros, calories, hydration, supplements, and meal-planning fundamentals.
- Cardio & Endurance
Running pace, heart rate zones, aerobic capacity, and endurance-training benchmarks.
- Recovery
Sleep, fatigue management, hydration, deloads, and recovery metrics that support consistency.
Contents
All 57 calculators on one pageStrength 13
- DOTS & Wilks Score Calculator DOTS & Wilks score calculator: compare powerlifting strength across weight classes with IPF DOTS and Wilks-2020 coefficients.
- DOTS vs Wilks vs GL Calculator Compare DOTS, Wilks, and Goodlift scores side by side to see which system rates your powerlifting total highest.
- Meet Day Attempt Selector Plan powerlifting meet attempts with opener, second, and third attempt suggestions based on 1RM and confidence.
- One-Rep Max Calculator Estimate one-rep max with Epley, Brzycki, and Lombardi formulas.
- Plate Loading Calculator Calculate which weight plates to load on each side of a barbell to hit your target weight in kg or lbs.
- Progressive Overload Planner Project lifting progression with weekly overload and planned deload cycles.
- RPE to Percentage Converter Convert RPE and reps to percentage of 1RM with a full interactive RPE chart based on the Tuchscherer table.
- Smolov / Sheiko / Texas Method Cycles Generate a Smolov base mesocycle, a Sheiko-style block, or a Texas Method cycle from a single 1RM input.
- Strength Percentile Calculator Find out where your squat, bench, deadlift, or OHP ranks against other lifters by bodyweight and sex.
- Strength Standards Calculator Rank your lifts from Beginner to Elite based on bodyweight ratios.
- Velocity-Based 1RM Estimator Estimate one-rep max from concentric bar velocity using published load-velocity profiles.
- Wendler 5/3/1 Planner Generate a 4-week Wendler 5/3/1 cycle from squat, bench, deadlift, and overhead-press 1RMs.
- Workout Volume Calculator Calculate total training volume and compare against optimal ranges per muscle group.
Running and cardio 13
- Calories Burned Calculator Estimate exercise calorie burn from body weight, duration, MET intensity, and incline.
- Cycling Power & FTP Zone Calculator Calculate your 7 Coggan power training zones from FTP or a 20-minute test result with W/kg ratio.
- Marathon Pace + Elevation Calculator Convert a target marathon time on a hilly course into the flat-equivalent pace you actually need.
- Race Time Predictor Race Time predictor: predict finish times across 5K, 10K, half marathon, and marathon from any known race result using Riegel's formula.
- Resting Heart Rate Calculator Assess cardiovascular fitness from your resting heart rate — how it rates for your age and sex, and the reading that rates Good.
- Run Training Paces Calculator Get personalized Easy, Tempo, Threshold, Interval, and Speed training paces from a recent race time using the Daniels VDOT method.
- Running Pace Calculator Calculate pace per km and mile and project race finish times from one run.
- Sweat-Rate + Electrolyte Marathon Plan Compute marathon sweat rate, fluid intake, and sodium replacement plan from a single training session.
- Swim Pace Calculator Calculate swim pace, total time, or distance with SWOLF and effort-zone context.
- Treadmill Pace Converter Convert treadmill speed to running pace with incline-adjusted flat equivalent, projected race times, and calorie estimates.
- VO2 Max Estimator Estimate aerobic capacity with the Cooper 12-minute run or Rockport 1-mile walk field tests.
- Walking Calorie Calculator Estimate calories burned from walking using speed, duration, body weight, and incline.
- Zone 2 Heart Rate Calculator Calculate your Zone 2 heart rate with Maffetone, Karvonen, % Max HR, and lactate threshold methods compared side by side.
Body composition 9
- BMI Calculator Calculate BMI quickly with a plain-language range explanation and limitations.
- Body Fat Percentage Calculator Estimate body fat percentage using the U.S. Navy circumference method.
- Female Athlete Formula Suite Apply female-specific corrections to FFMI, Mifflin-St Jeor BMR, max heart rate, and body-fat estimation.
- FFMI Calculator Calculate Fat-Free Mass Index to gauge muscularity and compare against natural benchmarks.
- Flexibility Score Calculator Estimate your flexibility percentile and rating from a sit-and-reach test score, adjusted for age and sex.
- Ideal Weight Calculator Compare Devine, Robinson, Miller, and Hamwi formulas as a realistic range.
- Lean Body Mass Calculator Estimate lean body mass using Boer, James, and Hume formulas from height and weight.
- Muscle Gain Potential Calculator Estimate your natural muscular potential with the Casey Butt model and see how close you are to your genetic limit.
- Waist-to-Hip Ratio Calculator Calculate waist-to-hip ratio and assess body composition using WHO guidelines.
Nutrition 10
- BMR Calculator Estimate basal metabolic rate and maintenance calories using Mifflin-St Jeor assumptions.
- Creatine Intake Calculator Estimate creatine maintenance and loading doses from body weight and training frequency.
- Food-to-Exercise Converter See how long you need to exercise to burn off any food, personalized by bodyweight.
- Hybrid Athlete Macro Split Get protein, carb, and fat targets for athletes who run + lift, with training-day vs rest-day split.
- Intermittent Fasting Window Planner Plan protocol-based eating and fasting windows with a 24-hour timeline and 5:2 day picker.
- Macro Calculator Convert calorie targets into protein, carbs, and fat grams for your goal.
- Macro Cycling Calculator Calculate different macros for training days and rest days with carb cycling for recomp, lean bulk, or cut goals.
- Protein Intake Calculator Get daily protein targets based on training level and goal.
- TDEE Calculator Estimate your daily energy expenditure with Mifflin-St Jeor + activity factors.
- Water Intake Calculator Calculate daily water intake based on weight, activity level, and climate.
Recovery 5
- Heart Rate Zone Calculator Calculate personalized training zones with the Karvonen method.
- HRV Deload Trigger Decide whether to deload from 7 days of HRV vs 30-day baseline using the Plews 2014 method.
- Sleep Calculator Calculate optimal bed and wake times based on 90-minute sleep cycles.
- Sleep Debt Calculator Track 7 nights of sleep to calculate accumulated sleep debt with a recovery timeline and quality assessment.
- Sweat Rate Calculator Calculate your personal sweat rate from pre/post-exercise weigh-ins and estimate fluid and sodium losses using ACSM guidelines.
Planning 7
- Body Recomposition Planner Plan body-fat reduction pace, deficit targets, and protein needs around a timeline.
- Calorie Deficit Calculator Estimate required daily calorie deficit for a target timeline and bodyweight change.
- Concurrent Training Interference Estimator Estimate strength, hypertrophy, and power gain attenuation from running while lifting (Wilson 2012).
- Detraining Decay Estimator Estimate 1RM loss across a layoff using the Mujika & Padilla detraining model.
- Hybrid Training Planner Hybrid training planner: build a weekly schedule that balances running and lifting with interference warnings and recovery guidance.
- Junk Volume Detector Junk volume detector: paste a multi-week CSV training log and identify sets that don't drive strength or hypertrophy.
- Race-Week Taper Planner Build a race-week taper using the Bosquet 2007 meta-analysis with distance-aware depth and weekly plan.
Worth reading
All 137 articles- Evidence-Based Hypertrophy Program: Sets, Reps, Frequency
Evidence-based hypertrophy program: 10-20 hard sets per muscle a week, 30-85% 1RM near failure, frequency to spread volume, per Pelland 2026 and Schoenfeld.
15-minute read, 12 sources
- Zone 2 Training: Find It With Lactate, Heart Rate, Talk Test
Zone 2 training sits just below the first lactate threshold. Find it with a lactate meter, heart rate or the talk test, and what 2025 reviews say it does.
13-minute read, 12 sources
- Protein for Muscle Gain: 1.6 g/kg (Morton 2018)
Morton 2018 placed the protein plateau at 1.6 g/kg with a 95% CI upper bound near 2.2 g/kg (49 studies, n=1,863). Cutting raises it to 2.3-3.1 g/kg lean.
12-minute read, 7 sources
Comparisons
All comparisons- Calorie Counting vs Intuitive Eating Diet for Weight Loss
Calorie counting vs intuitive eating diet: counting gives faster fat loss, intuitive eating protects maintenance. See who each fits and how to combine both.
- Is MyFitnessPal Accurate? TDEE Calculator vs MyFitnessPal
TDEE calculator vs MyFitnessPal: a calculator shows how your calorie target is built; a food logger tracks what you eat against it. How to use them together.
- How Accurate Is the Navy Body Fat Calculator vs Calipers
How accurate is the Navy body fat method? In 1,407 recruits, tape equations read 6 points low vs DXA and missed most fat loss; skinfolds erred by about 3.4.