Sports calculators & tools
42 free, instant calculators — pace, power, heart-rate zones, tournament builders, training load and more. Every formula is shown, sourced and explained. Nothing leaves your browser.
How these tools work
Running
8 toolsPace, prediction, zones and splits for road, track and trail.
Running Pace Calculator
Turn a distance and a time into pace per kilometre and per mile, plus speed. Deterministic and instant.
Race Time Predictor
Predict your time at a new distance from a recent result using Riegel's endurance model.
VO₂max Estimator (Cooper test)
Estimate aerobic capacity from how far you run in 12 minutes, using the classic Cooper test regression.
Training Pace Calculator
From your threshold pace, see educational easy, marathon, threshold and interval pace ranges.
Running Cadence Calculator
Work out your cadence in steps per minute, and your stride length if you add the distance.
Heart-Rate Zone Calculator
Build five Karvonen heart-rate zones from your age and resting heart rate.
Split Calculator
Get even-pace splits for any distance and target time — know exactly what each kilometre should read.
Marathon Time Predictor
Estimate your marathon finish from a recent shorter race with the Riegel model, including the halfway split.
Cycling
6 toolsPower, gearing, sizing and energy for the bike.
Bike Size Calculator
Get a starting frame-size range from your inseam for road or mountain bikes. A heuristic, not a fit.
Bike Gearing & Speed Calculator
See the speed a gear produces at a given cadence, plus gear ratio and metres of development.
Cycling Power Zones
Turn your FTP into the seven Coggan training zones, from active recovery to neuromuscular.
FTP Estimator
Estimate Functional Threshold Power from a 20-minute test, and see your zones and W/kg.
Cycling Calorie Calculator
Convert average power and ride time into work done (kJ) and an energy-burn estimate (kcal).
Ride Pace & Speed Calculator
Average speed and time-per-kilometre for a ride from distance and time.
Swimming
4 toolsPace, thresholds and splits for the pool.
Swim Pace Calculator
Pace per 100 m and speed from any swim distance and time.
Critical Swim Speed (CSS) Calculator
Estimate your sustainable swim threshold pace from 400 m and 200 m time-trials.
Pool Distance Converter
Convert swim distances and paces between metres and yards, exactly.
Swim Split Calculator
Even splits for a target swim — every 50 or 100 m mapped to a clock time.
Tennis & racquet
5 toolsGrip, string, balance and serve-speed helpers.
Tennis Grip Size Finder
Find your racquet grip size from the ring-finger hand measurement.
String Tension Guide
Understand how tension trades power for control, and which direction to try next.
Racquet Balance Explainer
Head-light or head-heavy? Convert a balance point into points and see what it means.
Match Duration Estimator
A rough estimate of how long a match runs from games played and average game length.
Serve Speed Converter
Convert a serve speed between km/h, mph and m/s, exactly.
Basketball
2 toolsShooting efficiency and possession estimates.
Football
2 toolsStandings, scheduling and shootout order.
Volleyball
2 toolsRotations and lineup systems made clear.
Golf
1 toolUnderstand the World Handicap System.
Tournament builders
5 toolsRound robin, elimination, Swiss and league schedules.
Round Robin Generator
Generate a full round-robin schedule by seed using the circle method, with byes for odd fields.
Single Elimination Bracket Builder
Bracket size, byes, rounds and total matches for any number of entrants.
Double Elimination Bracket Builder
Understand winners and losers brackets and the match counts for a double-elimination event.
Swiss Tournament Pairing Guide
Round-1 Swiss pairings and how many rounds you need for a given field.
League Scheduler
Fixtures, games per team and match-day rounds for a single or double round-robin league.
Training & health
7 toolsLoad, energy, hydration and recovery — educational estimates.
Training Load Calculator
Session load from RPE and duration, plus the acute:chronic workload ratio if you add your totals.
Rest Day Planner
A simple, honest guide to how many full rest days a week suits your training frequency.
Sweat Rate & Hydration Calculator
Measure your own sweat rate from body-weight change and fluid intake — the evidence-based method.
Calorie & TDEE Calculator
Estimate resting energy (BMR) and daily needs (TDEE) with the Mifflin–St Jeor equation.
Protein Intake Calculator
A daily protein range for your body weight and goal, from sports-nutrition position stands.
Energy Expenditure Calculator
Estimate calories burned for an activity using its MET value, your weight and time.
Recovery Time Estimator
A general window for how long to recover before hard training of the same muscles again.