Pace Calculator
Calculate running pace, finish time or distance — plus race predictions and splits
Results & Details
// Running Pace Zones
// Splits Table
| Split | Split Time | Cumulative |
|---|---|---|
| Calculate above to see splits | ||
// Race Time Predictions
// Estimated Calorie Burn
How the Pace Calculator Works
Choose what you want to find — pace, time or distance — enter the other two values, and the result appears instantly. The splits table shows your time at each kilometre (or mile) milestone at constant pace.
Pace Formulas
Pace Zones Explained
Easy / Recovery — conversational pace, used for recovery runs and long slow distance. Builds aerobic base. Aerobic — comfortable but purposeful. Most training volume should be here. Tempo — comfortably hard, sustainable for 20–60 minutes. Improves lactate threshold. Interval — hard effort, sustainable for a few minutes at a time. Builds VO2 max. Sprint — maximal effort, unsustainable beyond ~2 minutes.
The Riegel Race Prediction Formula
The Riegel formula predicts race times at other distances based on a known performance. It uses an exponent of 1.06 to account for the fact that longer races require proportionally more time per kilometre. For example, your 10K time multiplied by the distance ratio (raised to the power of 1.06) gives an estimate of your half-marathon time.
Running Pace: Conversions, Predictions, and Pacing Strategy
Built and verified by Andrius R. · Updated June 2026
Pace is the runner's exchange rate — between distance and time, between kilometers and miles, between today's 5K and the marathon you're eyeing. Here's the math, plus the strategy mistakes the math exposes.
The basic conversions
Pace = 25:00 ÷ 5 = 5:00 per km. Per mile: multiply by 1.609 → ~8:03 per mile. As speed: 12.0 km/h (7.46 mph). Common reference points: a 30:00 5K is 6:00/km (9:39/mi); a 4-hour marathon averages 5:41/km (9:09/mi).
Predicting race times: the Riegel formula
You can't just scale pace to longer distances — fatigue compounds. The standard prediction is Riegel's formula: T₂ = T₁ × (D₂ ÷ D₁)1.06. That exponent of 1.06 encodes how much humans slow as distance grows. From the 25:00 5K:
| Distance | Naive scaling (same pace) | Riegel prediction |
|---|---|---|
| 10K | 50:00 | ~52:07 |
| Half marathon | 1:45:29 | ~1:55:00 |
| Marathon | 3:30:58 | ~3:59:46 |
Important caveat: Riegel assumes you've trained appropriately for the longer distance. A sharp 5K runner with low weekly mileage will miss the marathon prediction badly — the formula extrapolates fitness, not endurance you haven't built.
Why even splits beat heroic starts
The most common racing error is banking time early — going out fast "while fresh." Physiology punishes this: running above your sustainable pace burns through glycogen and accumulates fatigue disproportionately, and the minutes lost in the late-race fade exceed the seconds banked early. Most distance world records have been set with near-even or slightly negative splits (second half faster). Practical version: run the first 10% of any race deliberately slower than goal pace feels, hit goal pace in the middle, and spend whatever's left at the end. Use the splits table this calculator generates as your per-km checklist.
Training paces: most running should feel too slow
A counterintuitive finding from elite practice: roughly 80% of effective endurance training happens at an easy pace — conversational, nose-breathable, typically 60–90+ seconds per km slower than 5K race pace. Easy volume builds the aerobic engine; the remaining ~20% (intervals, tempo runs) sharpens it. Runners who do every run at "medium-hard" improve slower and injure more. Your easy pace will feel embarrassingly slow; that's the sign it's right. Pair pace targets with effort checks using the heart rate zone calculator.
What realistically moves your pace
In rough order of impact: consistent weekly mileage built gradually (the 10%-per-week ramp guideline exists because injury is the #1 pace-killer), then time — aerobic adaptations compound over months and years, not weeks — then structured speedwork, then body weight, then gear. Beginners often improve a 5K by minutes in a season simply by running more and mostly easy; the exotic stuff is the last 2%.
From the Blog
// 80/20 Rule
80% of training runs should be at easy/aerobic pace. Only 20% at tempo or harder. Most runners run their easy runs too fast.
// Negative Splits
Running the second half of a race faster than the first (negative splits) is the most efficient race strategy for most distances.
// 10% Rule
Never increase weekly training volume by more than 10% week-on-week to reduce injury risk.
// Cadence
Most elite runners maintain 170–180 steps per minute. Higher cadence with shorter stride length reduces injury risk.