How do I plan pacing for an ultra marathon?

Start conservatively and expect to slow down. Most ultra runners fade 10-20% in the second half. Plan your early checkpoints with a buffer ahead of cut-off times. Use your training long run pace plus 15-20% as a starting guide. Walking uphills and running flats and downhills is standard ultra strategy.

What is a typical cut-off time for a 50 mile ultra?

UK 50-mile ultras typically allow 13-16 hours. Popular events like the South Downs Way 50 allow 13 hours. The Cotswold Way Century (100 miles) allows 30 hours. Each checkpoint has its own cut-off, usually calculated proportionally from the overall time limit.

How much time should I spend at checkpoints?

Keep checkpoint stops to 5-10 minutes for shorter ultras (50K) and up to 15-20 minutes at major aid stations in 100-mile races. Total time at checkpoints should not exceed 10-15% of your total race time. Have a plan for what you need to do at each stop to avoid wasting time.

What is fade factor in ultra running?

Fade factor is the expected pace slowdown over the course of a race due to fatigue, terrain and accumulated strain. A 10% fade means your final segments are roughly 10% slower than your opening segments. More experienced ultra runners have lower fade factors, typically 5-10%, while newer ultra runners may fade 15-25%.

RunCalcs

Ultra Checkpoint Calculator

Calculate checkpoint arrival times and cut-off margins for ultra marathons.

Race Distance

Select your ultra race distance

Checkpoints

Number of aid stations / checkpoints

Target Finish Time

Hours

Target time in hours

Minutes

Target time in minutes

Start Time

Hour

Race start hour (24h clock)

Minute

Race start minute

How We Calculate This

This calculator splits your race into equal segments between checkpoints and estimates arrival times using a progressive fade model.

Fade model

The calculator applies a quadratic fade: pace slows progressively as you cover more distance. A 10% fade factor means the final segment is approximately 10% slower than average. Earlier segments are correspondingly faster.

Cut-off margins

Cut-off times are calculated proportionally from the overall time limit. A positive margin means you are ahead of the cut-off; a negative margin means you risk being timed out.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always consult a coach or medical professional for personalised training advice.