ABOUT
About Race Pace Planner
Race Pace Planner is an independent project by Rai Ansar, a web developer in Pakistan who builds small, single-purpose tools. It turns a finish-time goal into checkpoint splits that add up exactly to that goal, and prints them as a pace band you can check with a ruler.
Why it exists
Most pace charts round the race: a marathon becomes 42 km or 26.2 miles, and mile tables stop at mile 26. Those shortcuts can shift a plan's finish by a few seconds or by more than a minute. This site keeps the full distances (42.195 km and 21.0975 km), includes the short final segment in every plan, and shows the arithmetic so you can check it.
It is not affiliated with any race, club, coach, watch brand or with the separate site race-planner.com. It is not a coach either: it calculates splits from the goal you enter.
How the calculations work
- Distances. Marathon 42.195 km, half marathon 21.0975 km, 10K and 5K as stated. One mile is exactly 1.609344 km.
- Average pace is goal seconds divided by distance, rounded to the nearest second only for display.
- Checkpoints are placed every kilometre, every 5 km or every mile, plus the exact finish. Each segment gets a whole number of seconds; leftover seconds go to the segments with the largest fractional share, so the elapsed column always ends exactly on your goal.
- Negative and positive splits change pace steadily from 2% slower than average at the start to 2% faster at the finish (reversed for positive), then scale the whole plan to your goal time. The 2% figure is our own illustrative choice, not a coaching standard.
- Run/walk repeats your run and walk intervals from the start gun and cuts the last cycle at the finish time.
Limits
- Hills, wind, heat, crowding and your fitness are not modelled. Even pace is not even effort.
- Courses are certified along the shortest possible route, and USA Track & Field notes that most runners do not run it, so a GPS watch usually records a longer distance than the certified course. Use the elapsed time at the course markers to pace yourself, not the watch's distance.
- Nothing here predicts what time you can run. For that you need your own training data or a coach.
- Printed sizes depend on your printer. The band carries a 50 mm ruler, so measure it on your printout to confirm the scale.
How pages are made
Page text is drafted with AI assistance (Anthropic's Claude) from the sources linked on each page and from a review of the pages that currently rank for each topic. Every number in every table is produced by this site's own calculator code when the site is built, and an automated test suite recomputes those rows independently before each release. Pages are checked against their linked sources before they are published. When a page changes in substance, its "Updated" date changes; a date is never bumped on its own.
Money
There are no ads or affiliate links today. If either is added later it will be labelled where it appears, and it will never change a calculation.
Contact
Found a wrong number? Email hello@racepaceplanner.com with the plan link from your address bar. See the contact page.
Sources
- World Athletics: marathon: marathon distance, 42.195 km.
- NIST: unit conversion factors: international mile, exactly 1.609344 km.
- USATF: position on GPS used by runners: courses are measured on the shortest possible route; GPS usually reads longer.
Last checked 24 September 2026.