Grams, kilograms, pounds and newtons in bridge contests

Short answer: contests quote loads in kilograms or pounds and bridge mass in grams, so convert to the same unit before computing efficiency. Strictly, kilograms and grams measure mass, and newtons measure force.

Conversions

Examples: 100 lb ≈ 45.4 kg. A 29 lb load ≈ 13.2 kg ≈ 129 N.

Mass and weight

Mass is how much matter something has, and is measured in grams or kilograms. Weight is the force of gravity on it, measured in newtons. Everyday speech and most contests say "weight" and mean mass, and the scale reads mass.

Keeping efficiency straight

Efficiency is load divided by the bridge's mass, so use the same unit for both. A 10 g bridge holding 10 kg is 10,000 g ÷ 10 g = 1,000. Mixing kilograms and grams gives an answer a thousand times off. See the efficiency score.

Check whether the scored load includes the bucket, hook or loading block. See how contests load a bridge.