Operating expense ratio calculator.

How this calculator works (the same math nouz uses)

The operating expense ratio is your "can I keep the lights on" number: the share of revenue swallowed by the cost of running the business — rent, payroll, utilities, software, marketing, supplies — but not the cost of the goods themselves. It's a single percentage that, read next to your gross margin, tells you whether the whole model actually leaves anything over. Lower is better: it means more of each euro of sales survives to become profit. The calculator also shows how many euros of revenue are left after operating expenses, which is the pool your COGS and profit have to share.

OpEx ratio = operating expenses ÷ revenue
Revenue left after OpEx = revenue − operating expenses

A worked example

Using the defaults — €38,000 monthly revenue and €16,000 of operating expenses — the ratio is 16,000 ÷ 38,000 = 42.1%. So about 42 cents of every euro goes on the cost of running the shop, leaving 38,000 − 16,000 = €22,000. That €22,000 isn't profit — it still has to cover COGS (the actual products) before anything reaches the bottom line. If food or stock cost eats, say, another €13,000, real profit is closer to €9,000. Splitting the two — cost of goods versus cost of operating — is exactly what stops the classic "we have plenty of customers but no money left" mystery.

What a healthy number looks like

Healthy depends heavily on your sector, so treat these as rough benchmarks rather than targets. Cafés and restaurants tend to run OpEx at 25–35% (which, with 30–35% food cost, gives a 60–70% prime cost); retail typically sits at 25–40% alongside a 50–60% gross margin; salons often land at 30–45% because labour is the product; and e-commerce runs 25–40%, excluding ad spend unless you treat it as a fixed cost. The 42% in the example is on the high side for most of these — workable, but a signal to watch rent and payroll closely. What matters more than hitting a number is the direction: a ratio drifting upward while revenue is flat is an early warning worth acting on.

Common mistakes

• Folding COGS into operating expenses. The whole point is to separate the cost of goods from the cost of running the shop — mixing them hides which one is the problem.
• Comparing across sectors. A salon's 40% and a retailer's 40% mean very different things because their gross margins differ; only compare like with like.
• Judging a single month. Rent and salaries are steady while revenue swings seasonally, so a quiet month spikes the ratio for reasons that have nothing to do with cost control.
• Trimming everything a little. The small lines aren't where the money is — meaningful improvement comes from the one or two biggest items.

When to use it — and what's next

Check this whenever revenue is fine but the bank balance isn't, and revisit it each quarter as costs creep. If you're above your sector range, there are really only two honest levers: cut the biggest line by around 10% (usually rent or staff hours), or grow revenue without growing cost in step (raise prices, lift the average ticket, sell more to existing customers). If pricing is your chosen lever, model it with the price increase impact calculator before you act. And to keep the ratio honest month to month, log costs and revenue as they happen in a daily profit and loss template. Nouz keeps operating expenses and COGS cleanly separated for you, so this ratio stays trustworthy without spreadsheet gymnastics.