Calculations for bicycle helmet drop tests
1. Drop Heights vs Joules
Calculated with a 5 kg drop mass.Drop Height Energy Falling Speed* =============== ====== ================ Meters Feet Joules KPH MPH 0.8 2.6 39 14.3 8.9 1.0 3.3 49 15.9 9.9 1.2 4.0 59 17.5 10.9 1.4 4.7 69 18.9 11.7 1.5 4.9 74 19.3 12.1 1.6 5.2 78 20.2 12.5 1.8 5.9 88 21.4 13.3 2.0 6.6 98 22.5 14.0 2.2 7.2 108 23.7 14.7 2.4 7.9 118 24.7 15.3 2.5 8.2 123 25.2 15.7
2. Joules vs Drop Heights
Calculated with a 5 kg drop mass.
Energy Drop Heights Velocity Falling Speed*
============== ============= ============= ================
Joules Ft-lb. Meters Feet M/Sec Ft/Sec KPH MPH
40 29.5 0.8 2.7 4.0 13.1 14.3 8.9
50 36.9 1.0 3.3 4.5 14.7 16.1 10.0
60 44.2 1.2 4.0 4.9 16.1 17.6 11.0
70 51.6 1.4 4.7 5.3 17.4 19.0 11.8
80 59.0 1.6 5.3 5.6 18.6 20.4 12.6
90 66.4 1.8 6.0 6.0 19.7 21.6 13.4
100 73.7 2.0 6.7 6.3 20.7 22.8 14.1
110 81.1 2.2 7.4 6.6 21.8 23.9 14.8
120 88.5 2.4 8.0 6.9 22.7 24.9 15.5
130 95.9 2.6 8.7 7.2 23.7 25.9 16.1
* Note that KPH and MPH relate primarily to the speed of the helmet hitting the pavement, not to the forward speed of
the bicycle or rider, unless the rider hits a concrete abutment. The typical bicycle crash impact occurs at a force level
equating to about 1 meter (3 feet) of drop, or a falling speed of 10 MPH. The rider's forward speed before the crash may be
considerably higher, but the speed of the head moving toward the ground, plus a component of the forward speed, less any energy
"scrubbed off" in other ways, normally average about 10 MPH. These calculations of course ignore the importance of rotational energy in a crash.We are indebted to the late Jim Sundahl for the extremely useful Excel spreadsheet to calculate these numbers.
Back to the top
Back to the Home Page