Cardio
Running Pace Calculator
Running pace calculator: calculate pace per kilometer and mile and project race finish times from your current run.
Result
Race times at this pace
Even pace held for the whole distance; not a prediction.
What does the Running Pace Calculator calculate, and which formula does it use?
The Running Pace Calculator converts a run's distance and time into pace per kilometre (time ÷ distance) and pace per mile (× 1.609344), then holds that pace constant to project finish times for the 5K, 10K, half marathon (21.0975 km), and marathon (42.195 km). It assumes an even effort, so it estimates splits rather than modelling how pace fades over longer races.
Last updated .
How to use it
- Enter a distance (km, or miles with Units set to US) and a time typed as m:ss or h:mm:ss to get the pace per km and per mile, the speed, and how long common races take at that pace. Use race-pace calculation for goal-setting and training-pace calculation for daily workouts — these are different numbers.
- Easy and long runs should feel conversational, well over a minute per mile slower than 5K race pace for most runners; the Run Training Paces Calculator gives your own paces from a recent race.
- Apply the 80/20 principle: 80% of weekly mileage at easy conversational pace, 20% at moderate-to-hard effort. This builds aerobic capacity while managing recovery cost.
- The race times shown hold your pace for the whole distance, which nobody quite does. To predict a race instead, Riegel's formula scales a 5K time by about 2.09 for a 10K, 4.60 for a half marathon and 9.59 for a marathon (the Race Time Predictor does this for any distance).
- Adjust for conditions: heat above about 60°F, wind above 10 mph, significant elevation and rain all slow your pace. Recalculate realistic targets for race-day conditions.
Questions people usually ask
How is pace calculated?
Pace is time divided by distance, and speed is the reverse. Enter a distance and a time and the calculator returns pace per kilometre and per mile, speed, and how long common race distances take at that pace.
Are the race times predictions?
No. They hold your pace constant over every distance, and real races slow down as the distance grows. For predictions, Riegel's T2 = T1 × (D2/D1)^1.06 scales a 5K time by about 2.09 for a 10K, 4.60 for a half marathon and 9.59 for a marathon; the Race Time Predictor does this for any distance.
How much slower should easy runs be?
Easy runs should feel conversational. In Daniels' VDOT tables, easy pace is well over a minute per mile slower than 5K race pace for most runners; the Run Training Paces Calculator gives your own easy, threshold and interval paces from a recent race.
Can I use it for treadmill runs?
Yes, for the belt speed. To compare a treadmill run with road running, the Treadmill Pace Converter adjusts for incline: a 1% grade matched flat outdoor running best in Jones and Doust (1996).
Is this medical advice?
No. This tool provides general fitness estimates and should not replace medical guidance.
Is this tool free and private to use?
Yes. AI Fit Hub tools are free, no-signup browser tools. Inputs stay in your browser unless you choose to share a URL.
The formula, worked through
- Formula Running Pace Formula: Riegel & VDOT Race Pace Conversion
Running pace formula: pace = time / distance in min per km or mile, plus Riegel's T2 = T1 × (D2/D1)^1.06 for race-equivalent pace. Worked 10K-to-half example.
- Formula Race-Week Taper Formula + Carb Loading (Burke)
Race-week taper formula: cut volume 41–60% over about 2 weeks while holding intensity and frequency (Bosquet 2007); performance usually improves about 3%.
- Formula Sweat Rate Formula
Sweat rate formula: (weight before − weight after + fluid drunk − urine) / hours. A worked 1-hour run, ACSM's 2% guidance and typical sweat sodium losses.
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Background on the Running Pace Calculator
- Comparison Swimming vs Running for Fitness
Swimming vs running for fitness: calorie burn, joint load, bone density and muscle use side by side, and which suits your goal and your joints.
- Statistics Marathon Statistics: Finishing Times, Demographics & Records
Marathon statistics: average finishing times, world records, age trends, training mileage and DNF rates, each figure with the source it comes from.
- Statistics Mobility & Injury Statistics: Risk Factors and Outcomes
Mobility and injury statistics: how common injuries are, risk factors, what interventions achieve and recovery times, each figure with its source.
- Statistics Running Statistics: Mortality, Performance, & Injury Data
Running statistics: mortality reduction, weekly mileage, injury rates, VO2 max norms and finishing-time benchmarks, each figure with its source.
Articles
- 8 min read How to Train for a 5k
A ten-week plan built around polarised training, aerobic base work, and a weekly VO2 max session — with pacing pulled from Riegel.
- 12 min read Marathon Pace and Elevation Adjustments
Marathon pace and elevation: a validated correction for total climb / descent — Strava grade-adjusted pace, Naismith's rule, where they break.
- 8 min read The Minetti Curve: Why Downhill Running Is Cheap Then Brutal
How Minetti's 2002 J Appl Physiol paper defines energy cost across grades, where the eccentric load tax dominates, and the practical pacing rule.
By goal
Use it from an agent or code
Any agent can run this calculator by URL: put the inputs in the query string and get JSON back, with the inputs that used defaults and a line to cite (add format=md for markdown). MCP clients reach it through https://aifithub.io/mcp.
https://aifithub.io/api/run/running-pace-calculator?distance_km=10&time_minutes=50
In code, import the same module; it runs where you import it, with no request or key.
import { compute } from "https://aifithub.io/engines/running-pace-calculator.js";Input and output contract, TypeScript types and the guide for agents.