Load chart provided by US Army Cold Regions Research and Engineering Laboratory (CRREL) to give a general guide for calculating ice strength.
MAXIMUM LOAD TABLE
Ice Thickness Maximum Load
2 inches One Person
4 inches One Person fishing, or a group walking
5 inches A snowmobile
8 inches A car
10-12 inches A light truck
WARNING!
This guideline is given to indicate what activity clear, solid, lake ice can
support with no strength-reducing factors. It is used to calculate short term
loads in motion. Always allow a conservative safety margin.
With brackish ice or river ice, double the required number of inches. River ice is considered only 85% as strong as clear lake ice, and salt or snow ice only 50% as strong.
If water is trapped between layers of ice, calculate only the thickness of the uppermost or outer most layer of ice to determine strength.
Ice requires constant cold temperatures to support the maximum load. If the outdoor temperature rises suddenly, the ice will weaken. If the temperature falls suddenly, the ice will harden again but not necessarily recover its original strength.