Running Pace & Race Time Calculator | Plan & Predict
Instantly calculate your running pace, average speed, finish time, and distance with our free suite of calculators.
Enter the distance ran or planned.
Format: MM:SS (e.g., 7:30)
Your Pace
--:--
per km
Time
--
Distance
--
Speed
--
Calories
--
Predicted Race Times Riegel Formula
| Distance | Predicted Time | Pace |
|---|
Training Zones Estimated Zones
| Zone | Pace (min/km) | Description |
|---|
How to Use This Running Calculator
Choose Calculation
Select "Pace" to find your speed, or "Race Predictor" to see potential times for new distances.
Enter Data
Input your recent time and distance. For Training Paces, use a recent race result.
Get Insights
View your pacing, speed conversions, and split times instantly.
Refine (Optional)
Add body weight to see calorie burn estimates or elevation to adjust for hills.
Running Pacing Strategies
Applying your calculator results to race day requires strategy. Here are the most common approaches:
- Negative Split: Start slightly slower than your goal pace for the first half, then accelerate. This is the gold standard for personal bests.
- Even Split: Maintain a consistent pace from start to finish. Best for flat courses like track races or flat marathons.
- Positive Split: Banking time early by running fast, accepting you will slow down. Often risky and painful in the final kilometers.
Understanding Your Training Paces
Easy Runs
60-70% effort. Builds aerobic base and aids recovery. You should be able to hold a full conversation.
Threshold
80-90% effort. "Comfortably hard." Improves your body's ability to clear lactate.
Intervals
95-100% effort. Builds VO2 max. Hard efforts lasting 3-5 minutes with rest in between.
Repetitions
Sprint pace. Improves running economy and speed. Short bouts (200-600m) with full recovery.
How Accurate Are Race Predictions?
What formula is used?
We use Riegel's Formula (1977), which is the industry standard: T2 = T1 × (D2 / D1)^1.06. It assumes you have trained appropriately for the specific distance you are predicting.
When are predictions less accurate?
Predictions lose accuracy when the target distance is more than 3-4x the input distance (e.g., predicting a marathon from a 5K time). Ultra distances (50km+) also introduce fatigue factors the formula cannot model perfectly.
Common Running Calculator Mistakes
- Ignoring Training Volume: A fast 5K time predicts a fast marathon, but only if you've done the long runs to support it.
- Overlooking Terrain: Hills slow you down. If your input race was downhill, your prediction for a flat course will be too fast.
- Training Too Fast: Many runners do their "easy" runs at "threshold" pace. Use the calculator to slow down your easy runs for better recovery.
Frequently Asked Questions
Why is my predicted race time different from my goal?
The calculator relies on past performance data. If your prediction is slower than your goal, it means you need to improve your fitness (VDOT) through structured training before you can realistically hit that goal.
Can I use this for walking?
Yes, the math works for any speed. However, walking mechanics are different, so calorie burn estimates may be slightly less accurate compared to running MET values.
What if my recent race was hilly?
Use the "Elevation Gain" input (in optional settings). Hills increase effort, so your "flat equivalent" pace is actually faster than your raw time suggests.