Scientific Toolbox
All 44 calculators, grouped by discipline. Each shows the formula it uses, where that formula comes from, and when it stops being accurate.
Health
Vitamin D Calculator
Estimate your sun exposure needs to reach optimal Vitamin D levels based on skin type and latitude.
Magnesium Calculator — Daily Requirement for Sleep and Recovery
Check your Magnesium intake and find your daily requirement to reduce anxiety and improve sleep.
Iron Needs Calculator
Especially important for female athletes. Calculate your daily iron requirement to prevent anemia.
Electrolyte Loss Calculator — Sodium, Potassium and Magnesium in Sweat
Estimate how much Sodium, Potassium, and Magnesium you lose during intense sweating.
Alcohol Metabolism Calculator
Predict how long until you are sober. "Zero to Hero" timeline based on drinks consumed.
Alcohol Calorie Calculator — What a Night Out Actually Costs
See the damage. Convert your night out into "Slices of Pizza" or "Miles to Run".
Caffeine Half-Life Calculator
Find out when your coffee leaves your system so you can sleep.
Melatonin Timing Calculator
Calculate the optimal time to take Melatonin for jet lag or sleep onset.
Sleep Cycle Calculator — Best Bedtime and Wake Time by 90-Minute Cycles
Find your optimal bedtime or wake-up time based on 90-minute REM sleep cycles.
Pregnancy Nutrient Needs
Calculate your trimester-specific nutrient requirements (Folate, Iron, Calcium) for a healthy baby.
Caffeine Metabolism Tracker
Scientific analysis of how your body clears caffeine based on genetics, smoking, and medication.
Pediatric Growth & Dosage
Comprehensive tracker for child caloric needs, high-protein growth targets, and safe medication dosages.
Pet Nutritional Optimizer
Calculate daily calories and water intake for cats and dogs based on age and activity.
Heat Index Calculator — Plus Wind Chill and UV Risk for Outdoor Training
Calculate Heat Index, Wind Chill, and UV safety for your next adventure.
Chronic Disease Nutrition Guide
Scientific dietary adjustments for common conditions like Diabetes, Hypertension, and CKD.
TDEE Calculator — Back-Calculated From Your Own Intake and Weight
Find your real TDEE from actual intake and weight data. No estimation formulas — back-calculated from your own body's response.
Sleep Performance Calculator for Athletes
Calculate your optimal sleep duration by sport, training load, and competition schedule. Evidence-based recommendations from NCAA and military performance research.
Menopause Nutrition Calculator — Perimenopause, Menopause & Post-Menopause
Calculate calorie and macro targets adjusted for your menopause stage. Three-stage formula for perimenopause, menopause, and post-menopause with bone health micronutrients.
BMR Calculator — Three Equations and the Spread Between Them
Calculate basal metabolic rate with Mifflin-St Jeor, Harris-Benedict and Katch-McArdle at once, and see how far apart they land on your numbers.
Sweat Rate Calculator — Measure Your Own Fluid Loss
Work out your sweat rate in litres per hour from a weigh-in, weigh-out field test, and get a drinking range that stays safely under your loss.
Steps to Calories Calculator — By Body Size, Not a Flat Constant
Convert steps to calories using your stride length and body mass, and see how far the usual flat 0.04 kcal-per-step constant misses for your size.
Strength
Body Fat Percentage Calculator
Calculate your body fat percentage using the US Navy method (circumference measurements) or BMI-based estimation. Includes athletic body fat benchmarks.
One Rep Max (1RM) Calculator
Calculate your one-rep max for squat, bench press, deadlift, and overhead press from any rep count using 5 validated formulas.
Wilks Score Calculator
Calculate your Wilks score and Dots coefficient to compare your powerlifting total across different body weights and between male and female lifters.
DOTS Calculator — Powerlifting Score by Bodyweight
Calculate your DOTS score from your squat, bench and deadlift total. Shows IPF GL and Wilks alongside it, because the three scales are not interchangeable.
IPF GL Points Calculator — Official IPF Scoring
Calculate IPF GL (Goodlift) points, the formula the IPF scores its own meets with. Separate curves for classic and equipped, powerlifting and bench-only.
FFMI Calculator — Fat-Free Mass Index and the Kouri 25 Anchor
Calculate FFMI and normalised FFMI from height, weight and body fat. Shows where you sit against the one figure that has a study behind it.
Natural Muscle Potential Calculator — Casey Butt Formula
Estimate your maximum drug-free muscle building potential using the Casey Butt formula. Enter height, wrist, and ankle measurements.
Grip Strength Calculator — Percentile and T-Score by Age
Compare a grip dynamometer reading against British normative data for your age and sex, with the T-score every published sarcopenia cut-off is actually built on.
Nutrition
Creatine Loading Calculator
Calculate your optimal creatine loading phase dosage. Maximize muscle saturation in 5-7 days.
Caffeine Pre-Workout Calculator
Determine your ideal caffeine dosage for peak athletic performance without the jitters.
Macro Calculator — Daily Protein, Carbs and Fat With a Meal Plan
Generate a personalised daily meal plan based on your macros. Set 1200–4500 kcal, choose high-protein, keto, vegan, paleo, or balanced, and get an instant macro breakdown.
Protein Calculator — Daily Intake for Muscle Gain
Calculate the exact protein needed to maximize muscle hypertrophy based on your weight.
Collagen Dosage Calculator — Therapeutic Dose for Joints and Skin
Find the effective therapeutic dose of collagen peptides for joint repair and skin health.
Keto Macro Calculator
Get your precise ketogenic macronutrient split: 75% Fat, 20% Protein, 5% Carbs.
Intermittent Fasting Calculator — 16:8, 18:6 and 20:4 Windows
Plan your eating and fasting windows (16:8, 18:6, 20:4) for optimal autophagy and fat loss.
Paleo Macro Calculator — Protein, Fat and Carb Split
Calculate your macro split for the "Caveman Diet" - high protein, moderate fat, low processed carbs.
Zone Diet Blocks Calculator
Calculate your daily "Zone Blocks" for hormonal balance (40% Carbs, 30% Protein, 30% Fat).
Energy Gel Calculator
Calculate how many energy gels you need for race day. Enter your duration and effort level to get a carb target, gel count, and timed fuelling schedule.
Carb Loading Calculator — 10–12 g/kg, and When Not To
Work out a carbohydrate loading protocol from the 2016 ACSM position statement: grams per day, per feed, pre-race, during, and the mass gain to expect.
Performance
Running Pace Calculator
Calculate your finish times for popular race distances (5K, 10K, Marathon) based on your pace.
Marathon Race Predictor
Predict your marathon time based on a recent race result (5K, 10K, Half) using the Riegel formula.
Heart Rate Zone Calculator
Calculate your 5 training zones based on Max Heart Rate or Heart Rate Reserve (Karvonen).
Target Heart Rate Calculator — Karvonen, %Max, MAF and Polarised
Find your target heart rate for any training intensity using heart rate reserve (Karvonen), percentage of max, the MAF 180 method, or polarised zones.
Max Heart Rate Calculator — And Why the Formula Is a Guess
Estimate maximum heart rate with the 220−age and Tanaka formulas, see the ±10–12 bpm error each carries, and how to test it instead.
Recovery Time Calculator — Hours Needed by Training Load and Sleep
Estimate how many hours of recovery you need based on training intensity and sleep quality.
Age Grade Calculator — 2025 USATF Road Tables
Age-grade any road time on the current 2025 tables. Shows the standard for your age, the open-class equivalent, and what the same grade is worth at every other distance.
MAS Calculator — Maximal Aerobic Speed and vVO2max
Work out maximal aerobic speed from a field test, with the interval paces it prescribes and an honest account of what the test does and does not measure.
Lactate Threshold Calculator — LTHR From a 30-Minute Test
Turn a 30-minute time trial into your lactate threshold heart rate and Joe Friel training zones, for running or cycling, without relying on a predicted maximum.
Heat Adjusted Pace Calculator — WBGT and What Heat Really Costs
Build WBGT from the ISO definition rather than a disputed regression, read the race-flag risk level, and see what heat measurably cost real marathon fields.
VO₂ Max Calculator
Estimate your VO₂ max from a field test (1.5-mile run, Cooper test, or submaximal step test) and see where you rank for your age and sex.
Cycling
Cycling FTP Calculator
Calculate your Functional Threshold Power (FTP) from a 20-minute test and get your 7-zone power training ranges.
What Is VAM in Cycling? VAM Calculator & Benchmarks
VAM (Velocità Ascensionale Media) measures your vertical ascent rate in m/hour. Calculate your VAM for any climb and benchmark against recreational and WorldTour pro levels.
Watts Per Kg Calculator — Power-to-Weight With Real Percentiles
Calculate W/kg at 5 seconds, 1 minute, 5 minutes and FTP, and see your percentile against real power-meter data rather than a disputed tier chart.
Cycling Gear Ratio Calculator
Calculate your gear development, speed at any cadence, and compare chainring/cassette combinations to find the optimal gearing for any terrain.
Cycling Calorie Calculator
Calculate calories burned cycling based on duration, power output, and body weight. Includes on-bike fuelling recommendations.
CdA Calculator — Drag Area from Power and Speed
Solve your drag area from a measured power and speed, with air density computed from pressure, temperature and humidity rather than assumed.
Crank Length Calculator — What the Evidence Actually Supports
Get the only published crank-length ratios there are, how little of the variance they explain, and the saddle-height change a new crank length actually requires.
Wealth
Compound Interest Calculator
Calculate how your investments grow over time using the power of compound interest. Plan your retirement with scientific precision.
Retirement Income Calculator: FIRE Number & Pension Gap
Calculate how much retirement income your portfolio can sustain. Includes pension gap analysis, safe withdrawal rate, and inflation-adjusted projections for UK savers.
Mortgage Calculator
Calculate monthly repayments, total interest paid, and amortisation schedule for any mortgage. Compare repayment vs interest-only strategies.