Cost Ratios: COGS, Labor and Overhead as a Percent of Sales

The basic cost ratio

cost ratio = cost ÷ sales × 100Use net sales, meaning after returns and discounts, and keep the same basis every month.

The ratios most owners track are:

• COGS ratio: cost of goods sold divided by sales. Subtract it from 100% and you have the gross margin.
• Labor ratio: total payroll cost divided by sales. Include payroll taxes and benefits if you pay them.
• Occupancy ratio: rent and related property costs divided by sales.
• Marketing ratio: advertising and promotion spend divided by sales.
• Prime cost ratio: COGS plus labor divided by sales. It is popular in food service, where those two items dominate.

Include a catch-all ratio for other expenses as well. When every cost has a ratio, the full list plus profit should add up to 100%, which gives you an easy way to spot a missing or double-counted item.

A worked monthly breakdown

A small business has 48,000 of sales in a month. Its costs are listed below with each ratio:

Writing the ratios down in one column makes the structure of the business visible at a glance: more than a third of every sale goes on the product, and almost a third on people. Two checks are worth doing. The cost ratios and the profit ratio should add up to 100%, which they do here: 37 + 30 + 10 + 5 + 7 + 11 = 100. And the gross margin is 100% − 37% = 63%.

Why ratios beat raw amounts

Next month sales rise to 60,000 and labor cost rises to 16,800. In absolute terms, wages went up by 2,400, which looks like a problem. As a ratio, labor fell from 14,400 ÷ 48,000 = 30% to 16,800 ÷ 60,000 = 28%, so the business actually used its staff more productively. The raw number moved one way and the ratio the other.

When you describe such a change, say it in percentage points: labor fell by 2 points, from 30% to 28%. The difference between percentage points and percent change matters here, because a 2-point drop is a 6.7% relative decline.

Fixed and variable costs behave differently

A ratio's behavior depends on the kind of cost behind it.

• Variable costs such as materials and packaging should stay close to a steady percentage of sales. If a variable ratio creeps up, look for waste, supplier price rises, extra discounting or a shift toward lower-margin products.
• Fixed costs such as rent do not change with sales, so their ratio falls when sales rise and climbs when sales fall. Rent of 4,800 is 10% of 48,000 in sales but only 8% of 60,000.
• Mixed costs like hourly labor move partly with sales. Watch their ratio over several periods rather than reacting to one month.

There is no single correct ratio for every business, since the mix of costs varies by industry and by how a business operates. The most useful benchmark is your own history, followed by comparisons with similar businesses using the same definitions.

Putting the ratios to work

1. Record the same categories every month so the ratios are comparable.
2. Calculate each ratio with the percentage calculator or a spreadsheet.
3. Look for a ratio that has moved by a point or two for several months in a row, then investigate the cause.
4. Set a target ratio and work out what it implies. If COGS is 17,760 on sales of 48,000 (37%) and you want 35%, the same costs need sales of 17,760 ÷ 0.35 = 50,743, which is about 5.7% more revenue, for example from slightly higher prices.
5. Use the margin calculator to check the resulting profit margin whenever you change a price or a cost.

This article is general education, not accounting or financial advice. Category definitions vary between businesses, so use the structure your accountant or your records require.