Running Pace Calculator & Race Time Predictor
Predict your 5K, 10K, half-marathon and marathon times with three models side-by-side — Riegel, Cameron and Jack Daniels VDOT — then get your Daniels training paces, grade-adjusted pace, Boston qualifier check, age grading and a negative-split race plan. Everything runs in your browser; no data ever leaves your device.
Race Time Predictor — 3 models, one input
Jack Daniels Training Paces (VDOT)
Grade-Adjusted Pace (GAP)
Boston Marathon Qualifier Checker (2026 standards)
Age-Grade Calculator
Negative-Split Race Planner
Why this predictor beats single-model calculators
| Feature | This tool | therunninggenie.com | fitliferegime.com | vdot-runner (GitHub) |
|---|---|---|---|---|
| Prediction models | Riegel + Cameron + VDOT, side-by-side | Riegel + Cameron | generic pace only | VDOT only |
| Model agreement analysis | Yes — spread shown honestly | No | No | No |
| Daniels training paces (E/M/T/I/R) | Yes | No | No | partial |
| Grade-adjusted pace (Minetti) | Yes | No | No | No |
| Boston qualifier checker (2026 stds) | Yes | No | No | No |
| Age grading (2025 tables) | Yes | No | No | No |
| Negative-split planner | Yes | No | No | No |
| Privacy (100% client-side) | Yes | unknown | unknown | Yes |
Comparison checked October 2026 against the public feature sets of each tool. Feature sets change; the table reflects what each site advertised at the time of checking.
How the three prediction models work
1. Riegel — the classic (1977)
Peter Riegel found that race times scale as T₂ = T₁ × (D₂/D₁)1.06. Double the distance and your pace fades ~6% (21.06 ≈ 2.085, not 2.0). Simple, robust, and the backbone of most race predictors. Weakness: the fixed 1.06 exponent over-predicts for elites and under-predicts for slower runners on long extrapolations.
2. Cameron — the refinement (late 1990s)
David Cameron fitted world top-10 performances to a variable-exponent model: T₂ = T₁ × (D₂/D₁) × f(D₁)/f(D₂), with f(x) = 13.49681 − 0.000030363x + 835.7114/x0.7905 (x in metres). The effective exponent shrinks for longer input races, mirroring real fatigue curves. Typically 1–3% closer than Riegel on 5K→marathon extrapolations.
3. Jack Daniels VDOT — the training-aware model
Daniels converts your race into a fitness score: oxygen cost VO₂ = −4.60 + 0.182258v + 0.000104v² (v in m/min) divided by the sustainable fraction %max = 0.8 + 0.1894393e−0.012778t + 0.2989558e−0.1932605t (t in minutes). That VDOT then predicts equivalent times at every distance and sets your five training zones. It is the only model here that also tells you how to train.
Frequently asked questions
How do I calculate my running pace?
Divide your finish time by the distance. A 25:00 5K is 25 ÷ 5 = 5:00 per km (about 8:03 per mile). The predictor shows your pace automatically for every predicted distance, in min/km or min/mile.
What is a good running pace?
It depends on distance, age and training. Using VDOT as a neutral yardstick: a 30:00 5K (~VDOT 35) is a solid beginner, 25:00 (~VDOT 40) a committed novice, sub-20:00 (~VDOT 50) a strong intermediate. Use the Age Grading tab for an age-fair comparison.
What is the Riegel formula for predicting race times?
T₂ = T₁ × (D₂/D₁)^1.06 (Peter Riegel, 1977). Your predicted time equals your known time scaled by the distance ratio to the power 1.06, modelling how fatigue compounds over longer races.
What is the Cameron running formula?
David Cameron's refinement uses a distance-dependent factor fitted to elite performances: T₂ = T₁ × (D₂/D₁) × f(D₁)/f(D₂), f(x) = 13.49681 − 0.000030363x + 835.7114/x^0.7905. It usually beats Riegel by 1–3% on long extrapolations like 5K to marathon.
What is VDOT and how does Jack Daniels calculate it?
Jack Daniels' fitness score from oxygen cost: VO₂ = −4.60 + 0.182258v + 0.000104v² divided by the sustainable %max for your race duration. One VDOT predicts equivalent times at all distances and generates your E/M/T/I/R training paces.
How do I find my marathon time from my 5K or half marathon?
Enter the shorter race in the predictor — all three models estimate your marathon (plus 10K, half and more) side-by-side. VDOT is the most training-aware; a wide spread between models means marathon endurance is the unknown.
What are Daniels training paces (E, M, T, I, R)?
Five training intensities from your VDOT: Easy (aerobic base, conversational), Marathon (your marathon race pace), Threshold (comfortably hard, ~1-hour pace), Interval (hard, ~VO₂max) and Repetition (fast, short reps). The Training Paces tab computes each with its purpose.
What is grade adjusted pace (GAP)?
GAP converts hilly pace to its flat equivalent with the Minetti (2002) energy-cost polynomial. Example: 5:00/km on a 5% climb ≈ 3:50/km of flat effort. Useful for trail runners comparing hilly runs to flat training paces.
What is the Boston Marathon qualifying time for my age?
2026 BAA standards (net): men 2:55/3:00/3:05/3:15/3:20/3:30/3:50/4:05/4:20/4:35/4:50 by age band from 18–34 to 80+; women 3:25/3:30/3:35/3:45/3:50/4:00/4:20/4:35/4:50/5:05/5:20. Non-binary uses women's standards. Meeting it only earns an application — recent fields filled minutes under the standard, so target a 5-minute buffer.
What is age grading in running?
Age-grade % = (age-group standard ÷ your time) × 100, using the 2025 USATF Masters tables (WMA methodology). ≥90% world class, ≥80% national, ≥70% regional, ≥60% local class. It also shows your open-class equivalent time.
Should I run negative splits in a marathon?
Yes — even or 1–2% negative splits beat banking time early in almost every analysis. The Split Planner builds per-5K splits for even, negative and positive strategies.
How accurate are race time predictors?
Between similar distances (10K → half), the three models usually agree within 1–2%. For 5K → marathon they can differ 3–5% — that spread is shown honestly here instead of hidden behind one number.
What is the difference between min/km and min/mile pace?
Multiply by 1.609 (5:00/km = 8:03/mile). The unit toggle above the tabs converts every table on this page instantly.
Can I use this for triathlon or trail running?
Yes — the models work for any distance, including triathlon run legs (choose Custom for exact metres). Trail runners should use the GAP tab to keep hilly efforts honest against flat training paces.
Is my data sent to a server?
No. All six calculators run locally in your browser. Nothing is uploaded, stored or tracked.