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Health & Fitness

Reddit-sourced calculators and references for the r/Fitness, r/loseit, r/GainIt, r/running, r/weightroom, r/Stronglifts, and r/sleep crowd — BMI, water intake, body-fat % (Navy), ideal weight, waist-to-hip, TDEE, calorie burn, protein requirement, macro split, HR zones (Karvonen), max HR (Tanaka), pace conversion, VO2max from 5K, 1RM (Epley/Brzycki), plate calculator, RPE → %1RM, warm-up sets, sleep cycle, caffeine half-life, sleep debt, training pace zones, race time predictor, and race splits.

33 tools available

Sub-categories

Wind Chill Calculator

Compute the felt-air temperature from wind speed and air temperature.

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BMI Calculator

Calculate Body Mass Index and see healthy ranges.

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Daily Water Intake Calculator

Get a personalized daily water target based on weight, activity, and climate.

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Body Fat % Calculator (Navy Method)

Estimate body-fat percentage from tape measurements and BMI.

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Ideal Weight Calculator (Devine / Hamwi / Robinson)

Compare the popular clinical ideal-weight formulas.

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Waist-to-Hip Ratio Calculator

Compute waist-to-hip ratio and the WHO health-risk band.

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TDEE & Macro Calculator

Calculate how many calories you burn per day and how to split them into protein, carbs, and fat.

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Calorie Burn Calculator

Estimate calories burned during exercise using MET formulas.

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Daily Protein Requirement Calculator

Get a protein target in g/day from body weight, lean mass, and activity.

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Macro Splitter (Carbs / Fat / Protein)

Split a calorie target into carbs, fat, and protein grams.

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Max Heart Rate Calculator (Tanaka)

Estimate HRmax from age with the Tanaka formula.

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Heart Rate Zone Calculator (Karvonen)

See your 5 training zones from resting HR and HRmax.

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Pace Converter (min/km ↔ min/mi ↔ km/h ↔ mph)

Convert running pace between metric and imperial units.

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VO2max Estimator from 5K Time

Estimate VO2max and equivalent race times from a recent 5K.

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One-Rep Max Calculator (Epley / Brzycki / Lombardi)

Estimate your 1RM from a sub-maximal set.

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Barbell Plate Loading Calculator

See exactly which plates to load on each side of the bar.

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RPE to %1RM Calculator

Convert Rate of Perceived Exertion to %1RM.

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Warm-Up Set Calculator

Build a smart warm-up ramp to your working sets.

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Sleep Cycle Calculator

Find the best bedtime or wake time based on 90-min sleep cycles.

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Caffeine Half-Life Calculator

Find out how much caffeine is still in your system at bedtime.

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Sleep Debt Calculator

See how much sleep debt you've accumulated and when you'll recover.

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Heat Index Calculator (NWS Rothfusz)

Get the felt-air temperature from heat and humidity.

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Running Pace Zones Calculator

Get easy / tempo / threshold / interval / repetition paces from a recent race or threshold pace.

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Race Time Predictor (Riegel)

Predict your 5K / 10K / half / marathon time from any other race result.

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Race Splits Calculator

Get per-mile or per-km splits to hit a goal finish time.

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Boston Qualifier Pace Calculator

What pace do you need for a Boston Qualifier at your age and gender?

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Labor Probability Estimator

Estimate the chance you'll go into labor this week.

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Heart-Rate Zone Calculator

Set Karvonen or Tanaka HR zones from age and resting HR.

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Race Time Predictor

Predict your finish time for any distance from a recent race.

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Maternity Benefit Net Pay

Estimate your net maternity benefit after the annualised tax rule.

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Cycle-Adjusted Due Date

Compute the EDD from LMP + cycle length or from a known conception date.

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NIPT False Positive Risk

What's the chance a 'high-risk' NIPT result is actually a false positive?

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First-Year Baby Cost Estimator

Estimate the total first-year cost of a baby in your city.

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