This race predictor scales a known race effort to other distances using Peter Riegel’s endurance equation (T2 = T1 x (D2 / D1)^1.06) and highlights Pelaris’s 0.5x to 2.0x distance guard-rail so you can see which projections are directly supported by your current durability.
Core Equation & Guard-Rail
T₂ = T₁ × (D₂ ÷ D₁)^1.06 · Supported Fence: 0.5× ≤ D₂/D₁ ≤ 2.0×
Pelaris only auto-projects race times between half and double the distance you actually ran (for example, 5K to 3K or 10K). Distances beyond 2.0x require specific long-run durability and fuelling verification.
46:55
4:42/km
1:43:30
4:54/km
3:35:48
5:07/km
| Distance | Projected [EST] | Pace / km | Pace / mi | Pelaris 0.5x–2.0x Fence |
|---|---|---|---|---|
| 1,500m | 6:17 | 4:11/km | 6:44/mi | Outside 0.5x Fence (0.30x distance) |
| 1 Mile | 6:46 | 4:12/km | 6:46/mi | Outside 0.5x Fence (0.32x distance) |
| 3K | 13:06 | 4:22/km | 7:02/mi | Supported Projection (0.5x to 2.0x) |
| 5K | 22:30 | 4:30/km | 7:15/mi | Known Effort Baseline |
| 10K | 46:55 | 4:42/km | 7:33/mi | Supported Projection (0.5x to 2.0x) |
| 15K | 1:12:06 | 4:48/km | 7:44/mi | Outside 2.0x Fence (3.0x distance) |
| Half Marathon (21.1K) | 1:43:30 | 4:54/km | 7:54/mi | Outside 2.0x Fence (4.2x distance) |
| Marathon (42.2K) | 3:35:48 | 5:07/km | 8:14/mi | Outside 2.0x Fence (8.4x distance) |
General fitness and training estimates only. Not medical advice.
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T₂ = T₁ × (D₂ ÷ D₁)^1.06 · Supported Fence: 0.5× ≤ D₂/D₁ ≤ 2.0×
Pelaris only auto-projects race times between half and double the distance you actually ran (for example, 5K to 3K or 10K). Distances beyond 2.0x require specific long-run durability and fuelling verification.
General fitness and training estimates only, labelled EST. Not medical advice or a clinical diagnosis.
Verified Literature
When a strong run at one distance hints at your time over another, that is Riegel's power law, drawn from world records from 100 metres out to 100 miles.
Riegel, P.S. "Athletic records and human endurance." American Scientist, 1981;69(3):285-290.
View the sourceYour VO2max estimate from a hard run comes straight from Daniels' VDOT tables, the pace-to-fitness model coaches have trusted for over forty years.
Daniels, J. Daniels' Running Formula, 4th edition. Champaign, IL: Human Kinetics, 2021. ISBN 9781718203662, 320 pp. Carries forward the VDOT tables and the velocity-to-oxygen-cost regressions first published in Daniels, J. & Gilbert, J. Oxygen Power: Performance Tables for Distance Runners, Tempe, AZ, 1979.
View the sourceDeep-Dive Training Guides
Automatic Tracking & Adaptation
Inside Pelaris, you never need to punch numbers into a spreadsheet. Every logged set, run and check-in updates your estimates automatically and adapts next week’s sessions.
Cardio & Endurance
VO2max & Fitness Age Calculator
Estimate VO2max from any run using Daniels VDOT, see your peer percentile in the FRIEND registry, and get a fitness age estimate plus your training paces.
Cardio & Endurance
Zone 2 Heart Rate Calculator
Calculate your Zone 2 heart rate ceiling across 4 sports-science models (Karvonen HRR, LTHR 80/20, %HRmax & MAF) plus your 80/20 weekly cardio budget.
Peter Riegel analysed world-record performances from 100 metres to 100 miles and found that doubling race distance slows average velocity by roughly 4 per cent, which corresponds to an exponent of 1.06 (2^1.06 = 2.085x total time).
High-mileage endurance runners with strong aerobic durability often hold pace closer to 1.04, while speed-biased athletes, field-sport players or low-mileage hybrid athletes typically slow closer to 1.08 over longer distances.
A fast 5K does not prove you have the glycogen storage, connective tissue resilience or aerobic durability for a 42.2 km marathon. Keeping automatic projections within 0.5x to 2.0x prevents a short run from writing an unrealistic marathon target.