Which costs stay fixed and which rise with sales?
Monthly rent and software subscriptions usually stay the same within a practical sales range. They are fixed costs. Materials, shipping, and payment fees tend to rise with each sale. They are variable costs.
Some expenses are mixed. A fulfillment service might charge a monthly base fee plus a per-order fee. Put the base fee in fixed costs and the per-order fee in unit costs, without counting either twice.
One sale contributes more than revenue
The useful amount is contribution: what remains of a sale after its variable costs and fees. A $25 sale with $10 product cost, a 4% payment fee, and a $1 fixed transaction fee contributes $13.
Divide monthly fixed costs by that contribution. With $1,000 of fixed costs, $1,000 ÷ $13 = 76.92. You need 77 whole sales to cover those costs.
What an unreachable break-even point means
If price does not cover variable costs and transaction fees, each extra sale contributes nothing or loses money. Increasing volume cannot cover fixed costs under those conditions.
Try a higher price, a lower unit cost, or different fee assumptions. Then check whether the required sales volume is achievable within your production and delivery capacity.
Plan beyond the threshold
Breaking even covers the costs you entered; it does not guarantee a comfortable income. Include appropriate payroll or owner compensation consistently, and compare higher volumes in the monthly profit calculator.
For a mix of products, use separate contribution calculations or a weighted average based on a stable sales mix. A shift toward lower-contribution products raises the number of sales needed.