Race Time Prediction
Riegel Formula
The classic endurance prediction model by Peter Riegel (1977). Uses an exponent of 1.06 to estimate how pace degrades over longer distances. Best suited for comparing distances that are reasonably close together.
Cameron Formula
An alternative model by Dave Cameron, built on how average speed falls with distance. More cautious than Riegel when predicting a marathon from a short race (e.g. 5K → marathon).
Aerobic Fitness
VO2max Estimator
Estimate your aerobic capacity from any race result using the Daniels & Gilbert formula (1979). No lab required — just a distance and a finish time. Includes a reference table of fitness levels.
Performance by Age (Performance by Age)
Comparing performances across ages and sexes.
Reference Tables
World Records
The fastest marks in road racing and middle distance history.
Pace Chart
A quick-reference table comparing min/km and min/mi with finish times for standard distances.
Pace and Speed Conversion
min/km, km/h, min/mi and mph — the formulas, a worked example and a reference table.
Environmental Impact
Environmental Adjustments
Learn how heat and altitude affect your running performance, based on marathon results (El Helou et al., 2012) and the NCAA altitude tables.
Try the Race Predictor
Compare Riegel and Cameron predictions side by side.
Try the VO2max Estimator
Estimate your aerobic fitness from a race result.
Running Science Guides: How to Use Performance Tools
These guides explain the science behind the calculators on Calcpace. Each one walks you through the research model, shows you how the numbers are calculated, and explains how to apply the results to real training decisions — from setting a marathon goal time to understanding how a summer heat wave is affecting your fitness.
The race prediction section covers the two most widely used formulas in recreational running. The Riegel formula (1977) uses a fixed power-law exponent and works well for adjacent distance predictions. The Cameron formula models how average speed falls with distance — it is more conservative than Riegel whenever the target is a marathon, whether from a 5K, a 10K or a half marathon, and agrees closely with it between neighbouring distances. Both guides explain when to trust each output.
The aerobic fitness section covers VO2max estimation and Age Grading. The VO2max guide uses the Daniels and Gilbert formula to turn any race result into an aerobic capacity estimate, with training zones derived from that number. Age Grading uses the 2025 road tables (Alan Jones, approved by USATF) to compare your time against the world record standard for your age and sex — allowing meaningful comparison across age groups, sexes, and decades of your own running history.
How does this work?
What is the difference between the Riegel and Cameron predictors?
Both predict race times across distances, but use different math. Riegel applies a fixed exponent (1.06) to all distances. Cameron uses a curve of how average speed falls with distance — making it more conservative when predicting a marathon from a 5K or a 10K. For adjacent distances (e.g. 10K to half marathon), they give nearly identical results.
Do I need an account to use the guides and calculators?
No — all public tools and guides are free with no account required. Creating a free account lets you log runs and track your progress over time, with a logged-in area that is 100% free of ads and ad trackers.
Which calculator should I start with?
If you have a specific race coming up, start with the Race Predictor using a recent race result. If you want a fitness baseline, use the VO2max Estimator. If you want to understand your performance relative to your age, use Age Grading. The Pace Chart is useful whenever you need to translate a training pace into a projected race finish time.