Calculators

Athens Marathon Split Calculator

Plan your Athens Marathon splits and get to know the course through the accompanying guide.

Free with a Training Plans account

Race Pace Calculator

Find the pace you need for your target time — or the finish time for a given pace. For 5K, 10K, half marathon, marathon or any distance you choose.

10K · 45:00 → 4:30/km

Pace Conversion Calculator

Instantly convert between km/h, mph, min/km and min/mile, and see the corresponding 5K, 10K, half-marathon and marathon finish times if you maintain the same pace.

12.0 km/h → 5:00/km · 8:03/mi

Pace Chart Calculator

Choose a distance and enter your time. See equivalent times over other distances at exactly the same pace, from 400 m to a marathon. Useful for intervals and race splits.

1000m · 3:10 → 400m 1:16

Race Predictor

Enter a recent race finish time to see predictions for other distances, from 1500 m to a marathon. Results are shown as an estimated range, not a certainty.

5K · 20:00 → 10K 41:42

Split Calculator

Choose a distance, target time or average pace, and race strategy — Even Pace or Negative Split. See every split from 5K to marathon or a custom distance, at 1 km, 5 km or your own interval.

10K · 40:00 · Negative 4%

Triathlon Finish Time Planner

Calculate your total triathlon finish time by adding swimming, T1, cycling, T2 and running. Choose Sprint through IRONMAN or custom distances, using pace /100 m, average speed or total time for each leg.

Standard (Olympic) → 2:35:00

Race Fueling Calculator

Calculate total carbohydrate grams for a triathlon or a single sport and organise your fuelling strategy.

Pre-start 30 g · Bike 2h 60 g/h · Run 1h 40 g/h → 190 g

GAP Calculator

GAP (Grade-Adjusted Pace) estimates the equivalent flat-ground pace for an uphill or downhill pace — or, in reverse, the expected pace on a given gradient at the same effort.

5:00/km · +5% → 3:55/km

Wind Pace Calculator

Calculate how headwinds, tailwinds or crosswinds may change your pace — or find the equivalent still-air effort for a pace you ran in the wind.

5:00/km · 3 Bft headwind → 5:16/km

Track Wind Calculator

Calculate how wind in a stadium affects your splits, or find the equivalent still-air split at the same effort.

0:40 / 200m · 3 Bft → 0:39

Heat-Adjusted Pace Calculator

Estimate the equivalent effort in ideal weather for a pace you ran in the heat — or see how much you may need to slow down as temperature and humidity rise.

5:00/km · 30°C 60% → 4:47/km

Swim Pace Calculator

Find the pace/100 m required for your target time over a swimming distance, or calculate your finish time from your average swim pace.

1500m · 25:00 → 1:40/100m

Threshold & CV Pace Calculator

Estimate threshold pace, Critical Velocity and VO₂max pace from a recent maximal race performance between 800 m and 10 km. See both the central estimate and the range observed among runners with similar performances.

5 km · 18:00 → 3:58/km

Running Pace Zones Calculator

Convert your threshold pace into Joe Friel’s 7 running zones, from recovery to anaerobic intensity.

4:00/km · 7 zones → 3:58–4:14

Critical Power Calculator

Calculate Critical Power (CP) and W′ from 2–4 maximal cycling efforts of different durations. Use the model to estimate watts for a given duration or duration at a given wattage.

3:00 400W · 12:00 320W → 293W

Cycling VO₂max Calculator

Estimate your VO₂max in ml/kg/min from the average power of a maximal 5-minute cycling effort and your body weight.

5:00 330W · 70kg → 58.4

Cycling Power Zones Calculator

Calculate Cycling Power Zones from your FTP using Andy Coggan’s system. See each zone’s boundaries in watts and, optionally, W/kg.

250W · 7 zones → 226–263

Heart Rate Zones Calculator

Calculate Heart Rate Zones from your Lactate Threshold Heart Rate (LTHR) using Joe Friel’s system, with different boundaries for Run and Bike.

170 bpm · Run → 146–151

Race Gearing Calculator

Find the chainring and cassette combination that best covers your climbing speed, main race speed and maximum pedalling speed at your chosen cadence. Alternatively, check whether your existing gearing covers those targets.

Tire Pressure Calculator

Calculate suggested front and rear tyre pressure from total weight, actual tyre width and diameter, surface, expected speed, casing category and bike type.

78 kg · 30 mm · some cracks → 4.85 / 4.70 bar

Critical Swim Speed Calculator

Calculate Critical Swim Speed (CSS) as pace/100 m from two maximal pool efforts over different distances.

400 6:20 · 200 2:50 → 1:45/100m

Swim Course Converter

Estimate equivalent pace/100 m between pools of different lengths, accounting for the different number of turns, stroke and assumed gain from each wall push-off.

1:30/100m · 25m → 1:31.6/100m