⚠️ Disclaimer: Race time predictions use the Riegel formula (exponent 1.06) and assume proper training for each distance. Actual times vary based on terrain, weather, fitness, and race-day conditions. Splits shown are even splits — adjust for hills or negative-split strategies.
How the Pace Calculator Works
This calculator supports three modes to help runners and walkers plan their training and races:
Pace Mode
Enter your distance and finish time to calculate your pace per mile or per kilometer. Great for reviewing a completed run or setting a benchmark.
Time Mode
Enter your distance and target pace to predict your finish time. Use this to plan race goals — for example, if you want to run a 5K at 8:00/mile pace, you'll finish in about 24:51.
Distance Mode
Enter your time and pace to find out how far you'll go. Useful for timed runs — "If I run for 45 minutes at 9:00/mile, how far will I get?"
The Riegel Formula
Equivalent race times are predicted using Pete Riegel's formula: T2 = T1 × (D2 / D1)^1.06. This accounts for the natural slowdown that occurs over longer distances. It's most accurate for trained runners racing between 5K and marathon.
Understanding Splits
The split table shows your target time at each mile or kilometer marker based on even pacing. Even splits are a reliable strategy, though many experienced runners prefer negative splits (running the second half slightly faster) to finish strong.
A good beginner running pace is typically 10–13 minutes per mile (6:15–8:00 per km). Most new runners start with a run/walk approach and gradually build speed. Focus on completing the distance before worrying about pace.
How does the Riegel formula predict race times?
The Riegel formula uses T2 = T1 × (D2/D1)^1.06 to predict race times. It accounts for the fact that pace naturally slows as distance increases. It's most accurate for distances between 5K and marathon.
What is negative splitting?
Negative splitting means running the second half of a race faster than the first half. Many elite runners use this strategy to conserve energy early and finish strong. Even splits (consistent pace throughout) are also effective.
How do I convert between pace per mile and pace per km?
To convert min/mile to min/km, divide by 1.60934. For example, 8:00/mile ≈ 4:58/km. Use the imperial/metric toggle in this calculator to switch instantly.
What's a good 5K time?
Average 5K times vary by age and fitness: beginners 30–40 minutes, intermediate 22–30 minutes, advanced under 22 minutes. Elite runners finish under 15 minutes (men) or 16 minutes (women).
How accurate are race time predictions?
The Riegel formula is generally accurate within 5–10% for trained runners racing similar distances. Predictions become less reliable when extrapolating from a 5K to a marathon, as longer races require different training adaptations.
What pace should I run for a sub-4-hour marathon?
To finish a marathon in under 4 hours, you need an average pace of about 9:09 per mile (5:41 per km). Enter your goal time and marathon distance in this calculator to see exact split targets.
Related Tools
More free calculators for health and everyday math.
About this page: Pace Calculator — Splits & Race Time Predictor is designed to help visitors make faster, better-informed decisions without creating an account or giving up personal data.
This page is designed for fast educational estimates. Results depend on the assumptions and inputs shown on the page and may differ from official statements, provider systems, or professional advice tailored to your situation.
Worked example: Example: run one conservative scenario and one aggressive scenario so you can understand the range of outcomes instead of relying on a single point estimate.
Last updated: March 9, 2026 · Author: CalcSharp Editorial Team · Reviewed by: CalcSharp Finance Review Desk
CalcSharp publishes free educational calculators and guides. We prioritize plain-English explanations, visible assumptions, and links to primary or official references wherever practical.