Running Pace & Race Time Calculator | Plan & Predict

Instantly calculate your running pace, average speed, finish time, and distance with our free suite of calculators.

What do you want to calculate?

Calculate Pace Calculate Time Calculate Distance Race Predictor

Distance

Enter the distance ran or planned.

Time (Duration)

Hrs

Mins

Secs

Your Pace

--:--

per mile

Time

Distance

Speed

Calories

Predicted Race Times Riegel Formula

Distance	Predicted Time	Pace

This calculator is free, fast and ad-free. No sign-up, and what you type in isn't sent to us.

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 the Race Predictor, use a recent race result.

Get Insights

View your pace, time, distance and speed 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.
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.

How Accurate Are Race Predictions?

What formula is used?

We use Riegel's Formula (1977): 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 much longer than the distance you entered (e.g., predicting a marathon from a 5K time). Ultra distances (50km+) also introduce fatigue factors the formula cannot model perfectly.

Note on Calorie Estimates: The calculator estimates calories as 0.97 kcal per kilogram of body weight per kilometer. That is the average J. L. Mayhew measured on a flat treadmill in nine trained male distance runners, and it did not change with running speed (Br J Sports Med, 1977). Because it was measured on the flat, elevation gain is not included in the calories: they are counted on the distance you actually ran. Elevation gain adjusts the pace and the time instead, as extra flat distance, except when you calculate distance. The rate comes from Naismith's rule, written in 1892 for hill walking: an hour for every three miles, plus an hour for every 2,000 feet of ascent (Scottish Mountaineering Club Journal, vol. 2, p. 136). That makes 1,000 m of climb worth 7.92 km on the flat. Actual burn varies based on individual metabolism, terrain, wind resistance, and running efficiency. Treat these numbers as a baseline estimate rather than an exact scientific measurement.

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.

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 through structured training before you can realistically hit that goal.

Can I use this for walking?

Yes, the pace math works for any speed. The calorie estimate uses the same rate per kilogram and kilometer at any speed, so treat it as a rough figure for walking.

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.