Profit Margin & Cost Ratio Calculator

＋More features: break-even point and net profit after fees

Break-even point (how many do I have to sell?)

From your fixed costs and the cost of each item, this works out the minimum number you must sell to avoid a loss — or, if you enter a target profit, the number needed to reach it.

Fixed costs (yen) Rent, wages, stall fees and anything else you pay even when nothing sells Variable cost per item (yen) Materials, purchase price and other costs incurred each time one item sells Selling price per item (yen) Target profit (yen — blank counts as 0)

Net profit on flea-market and online sales

Subtracts the selling fee and the shipping charged by marketplaces such as Mercari, to show the profit that actually stays with you.

Selling price (yen) Selling fee (%) Shipping paid by the seller (yen) Cost / purchase price (yen)

What this tool tells you

Enter what you sell for and what you paid, and see how much profit you make and what your profit margin is. It also answers the reverse question — “if I want a 30% margin, what should I charge?”. Useful for pricing in a shop, or for handmade and flea-market sales. All amounts are in Japanese yen.

How to use

Choose “Profit margin from price and cost” or “Selling price from a target margin”.
Enter the selling price and the cost (or the cost and your target margin).
As soon as both fields are filled in, the result appears — no button needed.

How it is calculated

Gross profit = selling price − cost
Profit margin (gross margin) = gross profit ÷ selling price × 100 (measured against the selling price) / Cost ratio = cost ÷ selling price × 100
Selling price from a target margin = cost ÷ (1 − target margin ÷ 100). Note that this is not the same as “adding 30% to the cost” (cost × 1.3).
Example: a cost of 600 yen with a target margin of 40% → 600 ÷ 0.6 = 1,000 yen (600 × 1.4 = 840 yen would give a margin of only 28.6%).

Sources and assumptions

This is an arithmetic calculation based on the definition of profit margin measured against the selling price.

Assumptions and notes

“Cost” here means the purchase price or materials. It does not include wages, rent or fees, so the profit margin is not the share that ends up in your pocket.
On flea-market apps and e-commerce sites you also have to subtract the selling fee (around 10%) and the shipping.
For restaurants in Japan a cost ratio of around 30% is often quoted as a rough guide, but it varies widely by type of business.

Frequently asked questions

What is the difference between a “profit margin” and “adding X% to the cost”?

They use different bases. Adding 30% to a cost of 600 yen (a markup) gives 780 yen, but that is a margin of 180 ÷ 780 = 23%. To reach a 30% margin you have to sell at 600 ÷ 0.7 = 857 yen. Confusing the two leaves you with thinner profit than you expected.

What profit margin should I aim for?

It depends on the business. Rules of thumb often quoted are 20–30% for retail, 60–70% for restaurants (a cost ratio of 30–40%), and three times the material cost for handmade goods (a margin of 67%). Judge by whether it covers your expenses and your working time.

Should I include consumption tax in the figures?

As a rule, keep everything tax-exclusive. Calculating with tax-inclusive prices makes the margin drift away from reality, so decide on one basis and stick to it.