Marathon Calculator

Marathon Race Time Predictor: Find Your Equivalent Race Times

Training for a marathon and wondering what your goal time means for shorter races? Our Marathon Race Time Predictor uses the well-known Pete Riegel formula (Runner’s World, 1977) to estimate how your marathon goal time translates to other popular race distances — from 5K all the way up to the full marathon.

This tool is perfect for runners planning race schedules, setting realistic goals, and understanding their current fitness level.

How the Marathon Predictor Works

The calculator is based on the Pete Riegel formula:

T₂ = T₁ × (D₂ / D₁)^1.06

Where:

• T₁ = Your goal marathon time
• D₁ = Marathon distance (42.195 km)
• D₂ = Target race distance
• T₂ = Predicted time for that distance

The exponent 1.06 accounts for the fact that longer races are more fatiguing per kilometer than shorter ones.

What You’ll Get

Predicted finish times for 10 different distances:

• 1,500 m
• 1 mile
• 3 miles
• 5K
• 5 miles
• 10K
• 15K
• 10 miles
• Half Marathon (21.0975 km)
• Full Marathon (your goal time)

Pace breakdowns for each distance:

• Minutes per kilometer (min/km)
• Minutes per mile (min/mi)

Why Use This Marathon Predictor?

• Set realistic goals for shorter races during marathon training
• Understand what a sub-4-hour or sub-3:30 marathon means for your 10K and half marathon times
• Track fitness improvement across distances
• Plan race schedule more intelligently

Example

Goal: 4:00:00 Marathon

Predicted Times:

• 5K → ~25:01
• 10K → ~51:45
• Half Marathon → ~1:55:07
• Full Marathon → 4:00:00 (as entered)

Pro Tips for Using the Predictor

• Use a recent race result as your input for more accurate predictions
• The formula works best for trained runners (not complete beginners)
• Real race times can vary based on course, weather, and fatigue
• Use predicted paces to guide your training runs

Combine with other SportyCalc tools:

• Use the Pace Calculator to turn predicted times into training paces
• Track overall fitness with the Fitness Age Calculator
• Monitor heart rate zones during training

Disclaimer: Race time predictions are estimates based on mathematical models. Actual performance depends on many factors including training, nutrition, weather, and course difficulty. This tool is for informational and planning purposes only.