The numbers, explained
Plain-English guides to the formulas behind the calculators: how each metric is worked out, a full worked example, and what the number does and does not measure. Educational, estimates only.
- Running
Age-Graded Running Performance Explained
Age grading turns a race time into a percentage of the standard for that age, sex and distance. A 49:30 ten kilometre is worked through to 70.7% at 58 and 53.3% at 24, with the two divisions behind it and the bands that read the result.
- Heart Rate Zones
Maximum Heart Rate: The 220-Minus-Age Formula and Its Limits
Maximum heart rate is a ceiling set mostly by age, not a measure of fitness. For a 55-year-old the three published formulas return 165, 170 and 158 bpm, and because zones are percentages that twelve-beat spread travels into every band built on top.
- Heart Rate Zones
Target Heart Rate: How to Find Your Training Range
A target heart rate is a percentage applied to a ceiling. On a 165 bpm maximum with a 60 bpm resting rate, moderate works out as 99 to 132 bpm by percentage of maximum and 102 to 122 by Karvonen, from the same person on the same day.
- Running
Running Cadence: What the Numbers Mean
Cadence is steps divided by minutes, and the same run can read 168 or 84 depending on whether both feet were counted. A 45-minute run of 7,560 steps is worked through to 168 spm, a 106.7 cm step and 10.75 km/h, with the origin of the 180 figure alongside.
- Running
Stride Length and Steps Per Mile Explained
A stride is two steps, and getting that factor of two wrong doubles or halves everything built on it. One lap of a track counted at 375 footfalls is worked through to a 106.7 cm step, a 213.3 cm stride and 1,509 steps to the mile.
- Running
Marathon Pacing: How to Split 42.195 km
A goal time divided by 42.195 km is one number; a pacing chart is that number laid out against every marker on the course. This guide works a 3:45:00 marathon through to 5:20 min/km (8:35 min/mile) and a full checkpoint table, shows why the unrounded pace has to survive to the last multiplication, and separates what the arithmetic settles from what it leaves to the race.
- Running
Treadmill Pace vs Outdoor Pace (and Incline Adjustments)
A treadmill shows speed and a training plan is written in pace, and the two are reciprocals: 60 divided by the belt speed. This guide works a 12.0 km/h belt through to 5:00 min/km and 8:03 min/mile, explains where the 1 per cent incline figure comes from and the speed range it was measured in, and keeps the exact unit conversion separate from the estimated effort comparison.
- Running
Running Splits Explained: Even, Negative and Positive
A split is the time for one segment of a run, and the pattern across segments is what an average pace hides. This guide sets out even, negative and positive splits, works a 50:00 ten kilometre through a 2 per cent negative split, and shows why thirty seconds is the whole of it.
- Running
How to Convert Running Pace Between min/mile and min/km
A mile is exactly 1.609344 km, so converting a pace is one division. The seconds are where it goes wrong. 8:30 per mile is worked through to 5:17 per kilometre, with a two-way reference table and the shortcuts that cost over a minute across a marathon.
- Running
The Riegel Formula: Predicting Race Times
The Riegel formula scales a known race time to any other distance using one fitted exponent of 1.06. Here is where that number came from, how to work the arithmetic by hand, and the distances at which the estimate starts to drift.