Break-even is the only number that tells you whether a slow month is a problem or just a slow month. Without it, every dip feels the same and you react to all of them the same way. With it, you know the line, you know how far above it you are, and you can say in one sentence what has to be true for the business to be fine.

It is also the number that makes pricing decisions obvious. Most owners discover, the first time they calculate it, that a one dollar price rise does more for survival than a week of extra selling, and that they have been working the harder lever for years.

Three numbers, and only three:

• Your average sale. Total revenue for a period divided by the number of sales in it. Not what you wish it was.
• What each sale costs you to deliver. Only the costs that exist because that sale happened: materials, packaging, the hours worked on it, card fees, delivery.
• Your fixed costs for a month. Everything that goes out whether you sell anything or not. Include the minimum you personally need to take out of the business, because a break-even that leaves you unpaid is not break-even.