Ice Thickness Load Capacity Calculator (Safe Ice for Walking, Snowmobiles & Vehicles)

How it works

Gold's formula: load (kg) ≈ A × h² with h in cm and A = 3.5 kg/cm² (conservative; 7 for cold, thick, sound ice) · white/snow ice counts at ½ thickness · growth: h² = h₀² + α² × freezing degree-days (α² ≈ 7.3 cm²/°C·day bare, 5 light snow, 2.5 heavy snow)

Ice carries a load by bending like a plate, and its strength grows with the square of its thickness, which is why a few extra centimetres matter so much and why the load tables jump from a person at ten centimetres to a truck at thirty-five. Only clear, hard-frozen ice earns full credit: the white ice that forms from refrozen snow or slush is riddled with bubbles and is counted at half, and grey, candled ice that has begun to melt from within is unsafe however thick. Ice grows by conducting heat up through itself into cold air, so it thickens fastest when thin and bare and slowest under an insulating blanket of snow, a relationship captured by counting the degrees below freezing accumulated over days.

Worked example

Fifteen centimetres of clear black ice supports about 790 kg by Gold's formula — fine for a snowmobile and rider at around 400 kg (roughly half the capacity, a sensible margin) but nowhere near the 25 cm a car needs. At −10 °C with no snow that ice grows about 2.3 cm the next day and reaches 25 cm in about 6 more days of the same cold; if 5 of the 15 cm were white ice it would count as only 12.5 cm and about 550 kg.

Frequently asked questions