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 run pace should be 60–90 seconds per mile slower than your current 5K race pace. Running all workouts at race pace is the most common cause of overtraining and injury in recreational runners.
- 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
Which formula is used here?
Converts a known distance and time into pace metrics, then projects race times using constant pace assumptions.
Can I use metric or imperial units?
Yes. This tool supports both metric and imperial units and remembers your preference.
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.
Do these tools replace medical guidance?
No. These outputs are general fitness estimates — not medical advice.
Can I switch between metric and imperial units?
Yes. Every tool supports both systems and remembers your preference in localStorage.
The formula, worked through
- Formula Running Pace Formula: Riegel & VDOT Race Pace Conversion
Running pace formula: pace = time / distance, plus Riegel T2 = T1 x (D2/D1)^1.06 for race-equivalent paces. Worked 10K-to-half-marathon example.
- Formula Marathon Pace Elevation Formula
Marathon pace elevation formula: about 1.5 s of finish time per metre climbed and 0.75 s back per metre descended, giving the flat-course pace your hilly goal equals.
- Formula Race-Week Taper Formula + Carb Loading (Burke)
Race-week taper math: cut training volume 41-60% over 8-14 days while holding intensity, then carb-load 7-12 g/kg (Burke 2011) for a ~3% faster race.
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Background on the Running Pace Calculator
- Guide How to Train for a 5K
Train for a 5K with this expert guide. Learn to build endurance, boost speed, and prevent injuries for your best race day performance.
- Comparison Treadmill vs Outdoor Running
Compare treadmill vs outdoor running for fitness, injury prevention, and performance. Discover the pros and cons of each, helping you choose the best.
- Examples Running Pace Examples
Learn to calculate and tune your running pace for various goals, from beginner 5Ks to marathon strategies and challenging trail ultra-marathons.
- Checklist Marathon Training Checklist: 16–20 Weeks to Race Day
A marathon training checklist from base to race day: a 16 to 20 week plan, long runs in race kit, fuel every 30 to 45 minutes, and a 2 to 3 week taper.
- Statistics Marathon Statistics: Finishing Times, Demographics & Records
Evidence-based marathon statistics: average finishing times, world records, age trends, training mileage norms, and DNF rates from peer-reviewed.
- Comparison Swimming vs Running for Fitness
Compare swimming and running for fitness side-by-side. Uncover which cardio workout is best for joint health, calorie burn, muscle engagement, and overall.
Articles
- 11 min read Endurance Training: The Evidence-Based Levers
Endurance training, ranked by evidence: intensity distribution, easy-day pace, VO2 max, and the taper, each linked to its deep dive on the science.
- 10 min read Riegel Formula Exponent 1.06 (Original 1981 Paper)
Riegel formula exponent 1.06 from the original 1981 American Scientist paper: T2 = T1 x (D2/D1)^1.06. Accurate for 5k-21k; raise to 1.10-1.15 for marathons.
- 13 min read Race-Time Prediction: VDOT vs Riegel Failure Modes
Race-time prediction failure modes: where VDOT, Riegel, and Cameron break — distance regimes, training-status assumptions, and prediction-error bands.
By goal
Use it from code
The same calculation as a JavaScript module you can import. It runs where you import it, with no request, key or rate limit.
import { compute } from "https://aifithub.io/engines/running-pace-calculator.js";Input and output contract, TypeScript types and the guide for agents.