The half marathon is 21097.5 meters — exactly half the marathon distance — which makes it awkward for any round interval: kilometer tables end with a 97.5-meter tail and mile tables with a 176-meter tail. The race split calculator keeps the finish line as the final row either way, so the table always sums to your target.
A 2:00:00 plan in kilometers
A 2:00:00 half marathon is a pace of 5:41.44 per kilometer. With 1 km intervals the table has 22 rows: 21 full kilometers plus the 97.5-meter finish segment. Cumulatives rise by 5:41 (occasionally 5:42 where rounding snaps) from 5:41 at the first kilometer to 1:59:19 at 21 km, and the finish row reads 2:00:00.
Reading it on race day: check the cumulative column at each kilometer flag. Being 30 seconds ahead at 15 km means exactly that — a fact to act on or ignore, not a prediction of the last 6 km.
The same plan in miles
With 1-mile intervals the table has 14 rows: 13 full miles plus the final 176.028 meters. Mile pace for 2:00:00 is 9:09 per mile, so the first 13 cumulatives run 9:09, 18:18, 27:27, and so on — mile 13 lands at 1:59:00 — before the short tail closes the plan at 2:00:00. Both tables describe the identical run; only the markers differ.
Which table to carry
Use the unit the course actually marks. Most half marathons mark every kilometer or every mile, and some mark both. A table with markers you will not see is dead weight; the cumulative column only works if you can compare it against something at a known distance.
Variations worth modeling
Two scenarios are worth a look before race day. First, a slightly positive start (a common reality when crowds hold you up): model it with the negative split calculator using a small negative q to see what the second half would have to do. Second, a negative-split plan: the same 2:00:00 with q = 12 runs the first half at about 5:47 per km and the second at about 5:36 per km, arriving at the same total. The arithmetic is the same; whether the distribution suits you is the part the calculator cannot decide.