Wind Pace Calculator

Air resistance uses about 8% of your energy at 6 m/s (2:47 per km) in still air, and it grows with the square of the speed of the air against you (Pugh, 1971). We hold your effort constant and solve for the pace you can hold into a headwind and with a tailwind. A tailwind gives back only about half of what the same headwind takes (Davies, 1980), which is why an out-and-back course in wind is always slower overall.

Forecast wind is measured 10 m above open ground. At running height it is about a third lighter in open terrain, and lighter again among buildings and trees. On a track you run into the wind on one straight and with it on the other, and it swings round you on the bends; we model each part of the lap and assume the wind blows along the straights, the worst case.

Both parkrun courses are treated as running due north–south on open ground. Lower Hutt goes 2.5 km south then 2.5 km back north. Waitangi Park goes north, south, north, south in four legs of about 1.25 km. Running in a group cuts your wind cost sharply, so treat these figures as the cost of running alone. The time lost slowing for each turnaround is not included, so Waitangi Park, with three turns, will run a few seconds slower than these splits.