What are the most important numbers in a restaurant?

We read a restaurant through four: food cost as a share of sales, labour as a share of sales, the true economics of the delivery channel, and the payback on the capital invested. The first two together form prime cost — the gauge that decides whether the model works — while delivery economics and payback catch the leaks and the structural questions the first two miss. Read together, weekly, they tell you almost everything that matters.

From How We Measure a Restaurant: The Four Numbers That Decide Profit — the full reading, with the method behind this answer.