Last Updated on November 10, 2026
Every business has a number of sales below which the month lost money. Most owners have never worked theirs out.
The usual mistake is judging a month by revenue. Revenue tells you how busy you were. It does not tell you whether the bills got paid, because every sale carries its own delivery cost before it contributes a penny to the rent.
This calculator takes your monthly fixed costs, your price and your cost per sale, and tells you exactly how many sales a month keep you above water, then shows the profit or loss either side of that line.
No email address, no sign-up. Everything runs in your browser and nothing you type is sent anywhere.
How the sums work
- Contribution per sale = price minus variable cost. This is what each sale actually puts towards the bills.
- Break-even sales = fixed costs divided by contribution, rounded up. You cannot sell two thirds of a job.
- Break-even revenue = fixed costs divided by the contribution share of the price.
Worked example, as an illustration: fixed costs of £2,400 a month, a typical sale of £60, and £24 of variable cost. Contribution is £36 per sale. £2,400 divided by £36 is 66.7, so 67 sales a month break even, at about £4,000 of revenue. Sale 68 is where profit starts.
The table under the result shows the months either side of the line. It is deliberately blunt: a month at 50 sales on those figures loses £600 no matter how busy it felt.
What this does not tell you
- It assumes one typical price and one typical cost. If you sell several very different things, run your main line first, or use a weighted average honestly.
- Fixed costs should include your own wage. A business that only breaks even by not paying its owner is not breaking even.
- It is a monthly snapshot, not a cash flow forecast. Timing of payments is a separate problem.
Who this is for
Any business with regular bills and a reasonably typical sale: trades, salons, cafes, makers, freelancers with productised services. If you have never known your number, you have been judging months by feel. The number replaces the feel.
Questions people ask
What is contribution and why not just use profit?
Contribution is the price minus only the variable cost of that sale. It measures what each sale puts towards fixed costs. Profit only exists after the contributions have covered all the fixed costs, which is exactly what the break-even point marks.
What counts as a fixed cost?
Anything that arrives whether you sell or not: rent, insurance, software subscriptions, salaries, loan repayments, your own wage. If a cost only happens because a sale happens, it is variable and belongs in the other box. If it is a bit of both, split it honestly.
My price is lower than my cost per sale. What now?
Then there is no break-even at any volume, and selling more makes it worse. Either the price rises, the delivery cost falls, or the line is dropped. The calculator will tell you this to your face rather than hide it.
Is my data stored?
No. The calculation runs in your browser. Nothing you type is sent anywhere.
- Profit margin calculator: get your contribution per sale right first.
- Marketing ROI calculator: break-even thinking applied to marketing spend.
- How to create a marketing budget: what to spend once you know your number.
