How this instrument works
Every sale carries two numbers: what the customer pays and what that particular unit cost you to make and deliver. The gap between them is the contribution margin, and it is the only money that ever reaches your rent, salaries and insurance. Divide the fixed block by that per-unit gap and you get the volume that closes it exactly — the point where profit is zero. Below it the firm is funding its overheads out of savings; above it, each further sale hands over the whole margin.
The formula is unforgiving about one thing: the margin sits in the denominator, so the relationship is a hyperbola rather than a line. On a $25 product costing $15 to produce, adding a single dollar to the price drops the required volume from 1,200 units to 1,091 — about 9% — and shaving a dollar off the variable cost does exactly the same. That asymmetry is why an hour spent on pricing usually outperforms an hour spent chasing extra orders at the current price.
Two cautions travel with the answer. Overheads are only fixed inside a capacity range: lease a second unit or start a night shift and the whole block steps up, so the figure must be recomputed at each step. And the result is a rate, not a deadline — 1,200 units is the crossover whether it takes a month or three years to get there, which is why the fixed figure entered is normally one month's worth, so the answer reads as units per month.
- Add up everything that bills on a schedule — rent, salaries, insurance, software, loan payments — for one consistent period, usually a month, and enter the total as Fixed costs.
- Put what a customer actually hands over into Price per unit: after any standing discount, before sales tax.
- Set Variable cost per unit to what one more unit costs you — materials, packaging, outbound shipping, card fees, piece-rate labour.
- Read Break-even units for the volume that clears the fixed block, and Break-even revenue for the same answer expressed in money.
- Round the unit figure upward before you use it. Four fifths of a chair cannot be sold, and a fractional unit is still short of covering the overheads.
Worked example — a $12,000 month at $25 a stool
A small furniture workshop carries $12,000 of fixed costs a month: workshop rent, two salaries, public liability insurance and a design subscription. A stool sells for $25, and the timber, glue, packaging and card fee behind it come to $15. The contribution margin is 25 − 15 = $10 per stool, so the crossover sits at 12,000 ⁄ 10 = 1,200 stools, worth 1,200 × 25 = $30,000 of monthly sales.
That $30,000 is not $30,000 of profit — it is the figure at which profit is exactly zero. Stool number 1,201 is the first one that pays the owner anything, and it pays $10. A good month of 1,500 stools therefore returns 300 × 10 = $3,000, not some proportion of the $37,500 that rings through the till.
Questions
What counts as a good break-even point?
There is no universal number — the honest test is whether that volume is reachable with the customers and capacity you already have. A workshop that needs 1,200 stools a month but has never shipped more than 400 has a pricing or cost problem, not a marketing problem. Compare the answer against your best recent month rather than against an industry average, and rerun it whenever a price or a supplier changes.
Should I include my own salary in fixed costs?
Yes, if you draw a set amount each month — that is the only way to see whether the business actually supports you. Leaving it out produces a flattering figure that quietly treats your labour as free, which is how founders end up subsidising their own company for years. If instead you take a commission on each sale, that pay belongs in Variable cost per unit, where it correctly narrows the margin.
What happens if the price is lower than the variable cost?
The sheet refuses to answer, and it is right to. When price fails to exceed variable cost the contribution margin is zero or negative, so every extra sale widens the loss and no volume ever clears the overheads. Arithmetically the denominator falls to zero and the answer runs off to infinity. The remedy is a higher price or a cheaper input — never more sales, which is the instinct the number exists to correct.
Does break-even revenue include sales tax?
No. Tax collected from a customer is money held on behalf of the state, not revenue, so enter the pre-tax figure in Price per unit. Card processing fees are the opposite case: they genuinely come out of your pocket on every transaction, so they belong in Variable cost per unit alongside materials and shipping.
How do I work out the volume for a target profit?
Add the profit you want to the fixed costs and run the sheet again. Wanting $5,000 of monthly profit on top of $12,000 of overheads means entering $17,000, which at a $10 margin gives 1,700 units instead of 1,200. The arithmetic is unchanged because a profit target behaves exactly like one more fixed obligation that has to be covered before anything is left over.
Why does my break-even point jump when I hire someone?
Because overheads are only fixed within a capacity range. A new salary lifts the fixed block on the day it starts, while the extra output and the sales to absorb it arrive later, so the required volume steps up before the capacity does. Recalculate at every step change — a new lease, a second shift, a machine payment — instead of treating one figure as permanent.
References
- U.S. Small Business Administration — calculate your startup costs
- U.S. Bureau of Labor Statistics — Business Employment Dynamics
- IRS — small business and self-employed tax centre
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.