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Running Pace Calculator

Calculate pace, predict race times via Riegel formula, and get training zones.

Run Details

Common: 5K = 5, 10K = 10, Half marathon = 21.1, Marathon = 42.2

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minutes

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Enter distance and time, then click Calculate

Methodology

Riegel Formula: T₂ = T₁ × (D₂ / D₁)^1.06. Published by Pete Riegel in Runner's World (1977). The exponent 1.06 accounts for physiological fatigue with distance. Best for distances within 2× of your training distance.

Training Zones: Based on Jack Daniels' VDOT system (Daniels' Running Formula, 3rd ed.). Easy (59–74% vVO₂max), Marathon, Threshold (~88% VO₂max), Interval (98% VO₂max), Repetition (105–120%).

FAQ

How does the race time predictor work?

Riegel formula: T2 = T1 × (D2/D1)^1.06. A 25-minute 5K predicts ~52-minute 10K. Accuracy decreases for distances far from your training distance.

What are training pace zones?

Based on Jack Daniels' VDOT: Easy (60–79% of race pace), Marathon pace, Threshold (lactate threshold, ~1-hr race pace), Interval (5K pace), Repetition (1-mile pace). Each builds different adaptations.

What is a good pace for beginners?

A comfortable conversational pace is typically 7–9 min/km (11–14 min/mile). The talk test: if you can speak full sentences, you're in the easy aerobic zone.

Get pace per kilometre and per mile, full split tables, training-pace zones, and race-time predictions for 5K, 10K, half marathon, and marathon distances.

How it works

Pace is simply finishing time divided by distance, but useful pacing also requires per-segment splits and consistent intensity.

Riegel's endurance formula extrapolates between race distances: t₂ = t₁ × (d₂/d₁)¹·⁰⁶. The exponent 1.06 captures typical aerobic fade-out with distance.

Training paces are usually expressed relative to a recent race or a threshold pace. Common zones: easy, marathon, threshold, interval, repetition.

Formulas

  • Pace: pace = time / distance — min/km or min/mile.
  • Riegel: t₂ = t₁ × (d₂ / d₁)^1.06 — Race-time prediction.
  • Split time: split = pace × segment distance — Even-pace splits.
  • Speed: speed = distance / time — km/h or mph.

Worked examples

5K → marathon prediction

Inputs: 5K in 22:00.

  1. Marathon (42.195 km): t = 22 × (42.195/5)^1.06
  2. t ≈ 22 × 9.66 ≈ 212 min
  3. t ≈ 3:32:00

Result: Predicted marathon ≈ 3 h 32 min, marathon pace ≈ 5:02/km.

Mile splits at 4:30/km

Inputs: Pace 4:30/km, distance 5 miles.

  1. 4:30/km × 1.60934 ≈ 7:14/mile
  2. 5 miles → 36:11

Result: Pace ≈ 7:14/mile, finish ≈ 36:11.

Use cases

  • Set a target finish time for a race
  • Build a split chart for a long training run
  • Convert between min/km and min/mile
  • Plan training paces (easy, threshold, interval)
  • Compare your fitness across different race distances

Common mistakes to avoid

  • Pacing the first 5 K too fast in a marathon
  • Confusing pace per mile with pace per km
  • Using Riegel for ultra-marathons (it under-predicts effort)
  • Ignoring elevation and weather when planning pace

Limitations

  • Riegel assumes consistent aerobic training
  • Real splits vary with terrain, weather, and fatigue
  • No fueling or hydration modelling
  • Track vs road vs trail differences not modelled

References

  1. Ainsworth BE et al. 2011 Compendium of Physical Activities. Med Sci Sports Exerc. 2011;43(8):1575–1581.
  2. American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 11th ed., 2021.
  3. Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate. Ann Med Exp Biol Fenn. 1957;35(3):307–315.
  4. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153–156.
  5. Riegel PS. Athletic records and human endurance. American Scientist. 1981;69(3):285–290.

Frequently asked questions

How is running pace calculated?

Pace = time ÷ distance. Convert between km and miles using 1 mile = 1.60934 km.

What is Riegel's formula?

t₂ = t₁ × (d₂/d₁)^1.06 — a statistical race-time predictor (Riegel 1981).

How accurate is Riegel?

Within ~3 % when input and target distances are within 3× of each other.

What is marathon pace?

It is your sustainable race pace for 42.195 km, typically 8–12 % slower than 10 K pace.

Can I plan negative splits?

Yes — use the splits table and assign descending paces to later segments.

Why are pace zones useful?

They keep training balanced — most volume in easy/marathon, less in threshold and interval.

Does the calculator handle imperial units?

Yes — pace per km and per mile are shown side by side.

Is the prediction guaranteed?

No. It is statistical — execution still depends on training and conditions.

Why do I fade in long runs?

Glycogen depletion, dehydration, and biomechanical fatigue. Riegel's 1.06 captures average fade.

Track vs road pace?

Typical track is 2–3 s/km faster than the same effort on a road race.

How fresh is the formula?

Riegel 1981 remains the standard endurance-prediction model.

Is this medical advice?

No — educational only.

Educational use only. Educational use only. The figures shown are population-level estimates from published exercise-physiology equations and may differ from your true values by 10–25%. Nothing on this page diagnoses, treats, prevents, or cures any condition. Consult a qualified healthcare professional before changing diet, exercise, or medication, especially if you have a heart condition, are pregnant, or take prescription drugs.

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