Split Calculator

Even splits vs. negative splits

An even split means the same pace from start to finish. A negative split means the second half is faster than the first. Both can reach the same finish time; the difference is where you spend your effort.

Starting slightly slower keeps something in reserve for the end, where races are won or lost. The cost is small: in a 2:00:00 half with a 2% faster second half, the first-half pace is only 6 seconds per mile slower than even pace.

How the tool spreads a faster second half

The calculator cuts the race at the exact halfway point. It gives the first half one pace and the second half a pace faster by the percent you enter, then solves both so they add up to your goal time.

With the default 2:00:00 half and 2%, that gives 9:15 per mile for the first half and 9:04 for the second, with 1:00:36 on the clock at halfway. The mile that crosses halfway mixes both paces, so its split falls in between.

How big should the difference be?

Keep it small. At about 9 minutes per mile, 1% is roughly 5 seconds per mile between the halves and 2% roughly 11 seconds. A larger number means a slow start and a hard finish to make up for it.

Enter 0 for even splits. The table under the tool lists even splits for a 2:00:00 half, mile by mile, so you can set the two plans side by side.

Using splits on race day

Splits are a guide, not a contract. For a single page of goal times by distance, see the half marathon pace chart or the marathon pace chart.

• Note a few key clock times instead of every split.
• Judge yourself over two or three miles, not one.
• Hills and water stops slow single miles; the plan is an average.
• Pick kilometer splits for races marked in km, or convert with the km to mile pace tool.

Related pages

Race Time Predictor, Running Cadence, Treadmill Incline Calculator, VO2 Max Calculator