Endurometry
Set goal pace from a recent 10K or half, not a number you like. Even or slight negative splits beat a fast first 10 km. Wear a pace band so you are not racing the watch.
Last updated October 5, 2026
Most marathon blow-ups are not fitness problems — they are pacing problems. You can be in sub-4 shape and finish in 4:20 because the first 10 km felt too easy to slow down. This page is about the boring, repeatable way to avoid that.
Start from a race you have actually run
Goal pace should come from evidence, not from a target you like the sound of. Take a recent race — a 10K or half marathon run in the last few months — and predict the equivalent marathon time with the race time predictor. The Riegel model behind it (T₂ = T₁ × (d₂/d₁)^1.06) is deliberately unkind: it assumes you have trained for the marathon distance. If you have not run further than 25 km in training, be honest and add a few minutes rather than subtracting them.
Two reference points worth memorising: a sub-4 marathon is 5:41/km (9:09/mile), and a sub-3 is 4:16/km (6:52/mile).
Even splits beat fast starts
Every strategy below finishes the same distance. What changes is where the cost lands.
| Approach | What it looks like | Typical outcome |
|---|---|---|
| Even splits | First km and last km at the same pace | Best finish for the fitness you actually have |
| Negative split | Second half slightly faster | Fastest possible — but needs a lot of discipline early |
| Positive split | First 10 km 10–15 s/km faster than goal | The classic: survival mode from 30–35 km, minutes lost |
The asymmetry is what matters. Banking 60 seconds in the first half rarely returns 60 seconds later; it usually costs two or three times that. The first 10 km should feel almost embarrassingly easy — that feeling is not a sign you are under-cooking it.
Fuel changes pace more than fitness does
From around 90 minutes onward, pace is limited by carbohydrate, not by willpower. Most runners need 60–90 g of carbohydrate per hour — roughly two to three gels, taken early and often rather than in one heroic lump at 30 km. Practise the exact gel and the exact timing on long training runs; race day is the wrong day to try a new flavour.
Hold pace without staring at your watch
Checking your watch every kilometre for three hours is a bad way to spend a marathon. Print a pace band, put it on your wrist, and read the split you need at each marker instead. Silicone reusable bands do the same job without a printer — worth it if you race several times a year.
The small things that cost minutes
Chafing at 30 km does not make you fitter, it makes you slower. Anti-chafe balm before the start and a pair of blister-free socks are the cheapest insurance in the sport. Neither is a performance product — they just remove two ways to lose time you have already paid for in training.
Related Tools
Race Time Predictor
Predict your finish time at any distance using the Riegel power law and the Daniels–Gilbert VO2max model.
Printable Pace Wristband
Generate a single-column pace wristband sized to your wrist — no cutting, just wrap it once. Pick even / negative / positive split and 1/2/5/10 km (or mi) intervals, then print at 100%.
Running Pace Calculator
Enter distance and finish time to get your pace per km and mile, average speed and per-kilometre splits.
Related guides
Estimate a marathon finish time
A practical workflow: scale a recent 10K or half with Daniels, add time if you have not trained the distance, then turn the finish into even-split pace.
How to Calculate Race Splits
Turn a goal finish into cumulative kilometre or mile splits, including the leftover 42.195 km row, and how that differs from a wrist pace band.
How to use a pace band
Card grid versus wrap-around wristband, 40 mm × wrist+2.5 cm, print at 100%, 5 km rows on a 4:00 marathon, and why you read course markers instead of GPS.
How the numbers are calculated
Frequently Asked Questions
Should I really run the first half slowly?
Run the first 10 km at goal pace or a few seconds slower. If you feel strong at halfway, you can pick it up — but do not plan on needing to.
Can I use a recent marathon to predict another one?
Only if the course and conditions were similar. A hot, hilly marathon is not a fair benchmark for a flat, cool one.
Do I need a GPS watch?
No. A printed pace band plus the kilometre markers gives you everything you need to hold even splits.
Want a new tool or fix?
Tell us which calculator, pace chart or fix would help — we build what runners ask for. Replies usually come back in 1–2 days.