Operating expenses (OPEX) calculator

Operating expenditure is the day-to-day cost of running the business beyond cost of sales: staff, sales and marketing, rent, software and admin.

The formula

OPEX = staff + sales and marketing + other running costs

Worked example: £39,000 a month

The example is a UK software company in one month: £50,000 of revenue excluding VAT, 400 customers and £180,000 in the bank.

£24,000 staff + £9,000 sales and marketing + £6,000 other = £39,000

Try it with your numbers

Work out your OPEX

Until you type a figure, the results show an example business. Fill in only what you know: from then on every result uses your figures alone, and nothing you type leaves your browser.

Your business numbers

Start with any one figure. Until you do, the results show the example business, whose figures are the grey hints in each box.

What this calculation uses

Turnover

Everything you invoiced in the period.

Staff costs

Salaries, employer National Insurance, pensions, freelancers.

Sales and marketing

Ads, sales salaries and tools.

Other running costs

Rent, software, insurance, admin.

Add more of your numbers

Open a group to fill it in. Everything you add shows up in the list below the calculator.

Sales and VAT

MonthQuarterYear

My turnover includes VAT

20%5%None

VAT you reclaim on costs

Input VAT on your purchases in the period.

Of which recurring

Subscriptions and contracts, excluding VAT.

Value of orders through your platform

Marketplaces only: what buyers paid in total.

Costs

Cost of sales

Costs that grow with each sale: materials, hosting, payment fees.

Depreciation and amortisation

From your accounts. 0 if you have none.

Interest paid

Corporation Tax

For the period, if you pay any.

Equipment and other capital spending

Things that last more than a year.

Customers and orders

Customers at the start

New customers

Customers lost

Number of orders

Or invoices, for a service business.

Recurring revenue over one month

MRR at the start of the month

Upgrades

Extra MRR from existing customers.

Downgrades

MRR lost from customers who left

Growth

Turnover in the previous period

The month, quarter or year before, on the same basis as your turnover.

Turnover in the same period last year

Cash

Cash in the bank

Cash received from customers

In the period, not what you invoiced.

Cash paid out for running costs

In the period, not counting equipment.

Balance sheet

Everything the company owns

Cash, equipment, money owed to you.

Everything it owes

Loans, bills, tax due.

Team

Hours your team works a week

Everyone added together.

Full-time hours a week

One investment or campaign

What you spent

On a campaign, a hire or a piece of kit.

What it brought back

Extra gross profit it produced.

Operating costs for the example

Example

£39,000

a month

£24,000 staff + £9,000 sales and marketing + £6,000 other = £39,000

Formula: Staff + sales and marketing + other running costs.

Staff share: 62%
Share of revenue: 78%

Everything your numbers show

For the example business: 29 of 29. Type your own figures to replace them. Select one for its page.

How to read your result

Staff is usually the biggest share in a startup. Opex as a share of revenue should fall as revenue grows.

Watch out for

Equipment you will use for years is capital spending, not opex.

Last checked 24 October 2026. Estimates only, not financial, tax or legal advice: check your accounts and documents, and take advice before you act. More terms in the startup glossary.