Ultramarathon Cutoff Strategy: How Much Buffer Do You Really Need?

How much cutoff buffer do you actually need in an ultra?

Enough that one bad section, one longer than planned aid station stop or one stomach problem does not suddenly turn the next checkpoint into a maths exam.

The less satisfying answer is that there is no magic number.

A two hour buffer might be comfortable on one part of a course and disappear surprisingly quickly somewhere else. Thirty minutes might be plenty late in a runnable race or nowhere near enough with a major climb, darkness and a long aid station still ahead.

The useful question is not simply “Am I ahead of the cutoff?”

It is “What does the buffer I have now need to survive before the next one?”

A cutoff is not your pace target

Cutoffs exist to control the race and keep runners moving through the course inside the event’s operational limits. They are not necessarily telling you how the organiser thinks you should pace the race.

Western States makes that distinction very clearly. Its current participant information says runners must leave aid stations before the designated cutoff and specifically notes that the cutoff times are not intended to be a pacing guide.

That matters because a cutoff can be generous early and much more meaningful later. Running the first third of the race purely to stay hours ahead of an early cutoff can create a completely different problem deep into the race.

The better approach is to start with the race you intend to run, then check whether that plan gives you enough room against the official constraints.

The finish cutoff is only one cutoff

It is easy to look at a race with a 30 hour finish cutoff, choose a 28 hour target and decide you have two hours in hand.

That does not mean you have two hours of useful buffer everywhere on the course.

An intermediate checkpoint can be much tighter relative to your planned schedule. The course may also put difficult terrain, a long night section or a major aid station immediately before that checkpoint.

This is why I prefer to look at the race checkpoint by checkpoint rather than thinking of cutoff buffer as one number attached to the finish.

You can be comfortably inside the overall race limit and still have one point in the middle of the course where the plan has almost no room to move.

Arrival cutoff or departure cutoff?

This is one of the easiest details to miss when building a race plan.

An arrival cutoff means the relevant question is whether you reach the checkpoint before the deadline.

A departure cutoff means arriving before the deadline is not enough. You still need to complete whatever you are doing at the aid station and leave before the stated time.

UTMB Mont-Blanc’s current regulations are explicit about this. Its time barriers apply to leaving the main aid stations, and runners must leave before the cutoff regardless of when they arrived. Western States uses the same leave before rule for its aid station cutoffs.

The difference can be small on paper and very large when you are actually racing.

If the checkpoint is a leave by cutoff at 18:00, you arrive at 17:40 and have a planned 15 minute stop, your useful buffer is not 20 minutes.

Your planned departure is 17:55.

You have five minutes.

What cutoff buffer actually means

Cutoff buffer is simply the amount of planned time between the relevant point in your schedule and the official deadline.

For an arrival cutoff:

For a departure cutoff:

The calculation is easy. The hard part is deciding what you expect that number to protect you from.

A 40 minute buffer might need to absorb a slow technical descent, an unexpected toilet stop and five extra minutes at an aid station. Another 40 minute buffer might sit before a simple runnable section where very little is expected to change.

Those are not the same planning situation even though the number is identical.

There is no magic safe cutoff buffer

I could not find a credible research based rule that says every ultrarunner should carry 30 minutes, one hour or two hours of cutoff buffer.

That makes sense. The right amount depends on too many things that are specific to the race and the runner.

This is why I would not build a race plan around one fixed buffer rule.

Instead, look at each checkpoint in the context of what comes before it and what you expect to happen there.

Stopped time is still race time

This is where cutoff strategy and aid station strategy become the same problem.

The race clock normally keeps running while you refill bottles, change socks, use the toilet, look for a drop bag or sit down to eat.

If you arrive thirty minutes ahead of the plan but spend twenty extra minutes at the checkpoint, most of that advantage has gone before the next section begins.

For a departure cutoff, the relationship is even more direct because the stop itself is inside the cutoff calculation.

This does not mean every aid station should be rushed. Sometimes spending ten extra minutes fixing your feet or getting food down is the best decision you can make.

The important part is that the plan recognises the time.

If you have not already planned the operational side of your stops, the related Guide Planning Your Ultramarathon Aid Station Strategy goes into that in more detail.

Should you bank cutoff time early?

Being ahead of a cutoff is obviously useful.

Deliberately increasing your early effort just to create a bigger number on the clock is a different thing.

Published ultramarathon pacing research gives good reason to be cautious with the idea that starting harder automatically buys useful time later. A study of 13,829 UTMB results found that more even pacing was associated with faster finishing performance. A separate 100K study found that the best finishing group ran at lower relative speeds through the first 30 kilometres than the slower groups, then maintained their performance better later.

Those studies do not prove that one pacing strategy is right for every mountain race. Terrain matters, conditions matter and association is not causation.

What they do show is that the simple idea of “go faster now so I can afford to slow down later” should not be treated as free time.

If the only way your race plan creates a comfortable buffer is by making the opening hours harder than you actually want to run them, I would take another look at the plan.

Find the checkpoint where the plan is actually tight

The easiest way to understand cutoff risk is to stop looking at the average buffer and find the smallest one.

In that example CP2 is the real constraint.

The plan is forty minutes clear at CP1 and fifty minutes clear at CP3, but the twenty minute stop at CP2 leaves only ten minutes against the leave by cutoff.

That is the checkpoint I would want to understand before race day.

What does the section into it look like? Is it likely to be in darkness? Is crew there? Does the planned stop genuinely need twenty minutes? Is that the point where shoes, lighting or clothing change? What happens if the previous section takes fifteen minutes longer than planned?

Those questions are much more useful than knowing the race has an average cutoff buffer of thirty three minutes.

Plan for the section after the checkpoint as well

A cutoff is not only about reaching one checkpoint.

If you use almost all of your available time getting there, you still need to be able to leave and complete the next section.

This is particularly important at a major aid station. Arriving just before a departure cutoff with empty bottles, no food and a mandatory gear change does not create a sensible next section simply because you technically arrived in time.

A race plan should therefore look beyond the deadline itself.

You want enough room to meet the rule, do what genuinely has to happen and leave ready for the terrain that follows.

When the buffer starts disappearing

Late in a race it is very easy for the numbers to become emotional.

You were an hour ahead. Now you are forty minutes ahead. Then twenty five. The instinct can be to start chasing the clock immediately.

Before doing that, work out why the buffer changed.

• Was one section slower than planned? Check whether the terrain or conditions explain it.
• Did an aid station run long? That may be a one off cost rather than evidence that every future section will be late.
• Is the runner consistently slowing? A repeated trend matters more than one difficult leg.
• What comes next? A runnable section and a long technical climb do not offer the same opportunity to recover time.
• What stop still has to happen? Do not pretend the next checkpoint takes zero minutes if food, clothing or feet still need attention.
• What does the rule actually require? Arrival and departure cutoffs are not interchangeable.

The aim is not to protect the original race plan at all costs. The race has already happened differently from the plan.

The aim is to understand the new situation clearly enough to make the next useful decision.

What the crew needs to know

Cutoffs should not live only in the runner’s head.

A crew supporting a long ultra should know which checkpoints are meaningful constraints and whether the runner needs to arrive or leave before the deadline.

For each important checkpoint I would want the crew to have:

• The official cutoff time.
• The cutoff rule. Arrive by or leave by.
• The planned arrival.
• The planned stop time.
• The planned departure.
• The planned buffer.
• The jobs that genuinely need to happen before leaving.

That gives the crew context if the runner arrives later than expected.

It also avoids the worst version of cutoff maths: several tired people standing beside a drop bag trying to decide whether the cutoff means arrival or departure while the clock keeps moving.

Where Track3D Race Planner fits

Track3D Race Planner lets the cutoff sit inside the same schedule as the course, checkpoints, stop time and target finish.

For each checkpoint you can record the cutoff and specify whether it applies to Arrival or Departure (leave by).

That distinction changes the buffer calculation. An arrival cutoff is compared with the planned arrival. A departure cutoff is compared with the planned departure after the checkpoint stop has been included.

Course-Aware Pacing then uses those constraints when distributing the target moving time across the course. Race Strategy also respects them when reshaping the early and later schedule.

The useful part is that changing a planned stop does not live in isolation. If you add ten minutes to a major aid station, the departure moves and the remaining cutoff buffer becomes visible.

The Race Plan and Runner Summary can then show the relevant Arrive by or Leave by deadline instead of presenting every cutoff as though it means the same thing.

Track3D still does not tell you whether you are physiologically capable of the finish target. You choose the target. The planner helps make the timing consequences of that target, the terrain, the stops and the cutoffs visible.

A practical cutoff planning checklist

Common ultramarathon cutoff questions

Build the buffer before race day

Cutoffs are one of those things that are simple until they are suddenly not.

On paper it is a time on a page. Deep into an ultra it can become the number that controls every decision for the next few hours.

The best time to understand it is before the race.

Know what the official rule means. Put the cutoff beside your planned arrival or departure. Include the stops you actually expect to make. Find the point where the plan is tight and work out what that buffer needs to survive.

Then race the course, not the cutoff clock.

Related guides:
How to Plan Your Race Day for a 100K or 100 Mile Ultramarathon
Planning Your Ultramarathon Aid Station Strategy
Ultra Marathon Crew Checklist

Race rules and research examples referenced in this Guide were checked against current public sources at the time of writing. Western States 2026 requires runners to leave aid stations before the designated cutoff and states that its cutoffs are not intended as a pacing guide: Western States Participant Guide. UTMB Mont-Blanc 2026 states that time barriers apply to leaving main aid stations and that runners must leave before the cutoff regardless of arrival time: UTMB Mont-Blanc Regulations. Pacing discussion references the UTMB 2008 to 2019 analysis of 13,829 results and the published 100K pacing study: UTMB pacing study and 100K pacing study. These studies describe associations in their studied populations and should not be treated as a universal pacing prescription. Always check the current rules and instructions for the event you are racing.