Day Rate Calculator

How to use this calculator

1. Pick the directionConverting a rate into an income tells you what a contract is worth. Converting a salary into a rate tells you what to charge to be no worse off, which is the harder and more useful question.
2. Be honest about billable weeksThis is the input that dominates the answer. 52 weeks is fantasy. 46 is optimistic for a first year. The gap between contracts is real and is what most first-time contractors underestimate.
3. Add your business costsAccountancy, insurance, equipment, training and professional subscriptions come out of the rate before anything reaches you. Three to five thousand a year is common.
4. Read the sensitivity lineThe working shows what four fewer billable weeks does to the answer. It is usually a larger effect than a fifty-pound change in the rate.

How the calculation works

Converting a day rate to income is multiplication, and the only judgement is how many days you will bill. There are 260 weekdays in a year. Subtract holiday, bank holidays, illness and the gap between contracts and 230 is a realistic working figure — roughly 46 weeks.

The reverse direction is where the interesting arithmetic sits, because a salary is not the whole package. An employer also contributes to your pension, pays you while you are on holiday, and pays you when you are ill. Comparing a day rate against a bare salary figure systematically flatters the contract.

So the calculator loads the salary before dividing. A £65,000 salary with 5% employer pension is worth £68,250. Add the value of 28 days paid leave — 28 of 260 working days, so about 10.8% — and it is worth roughly £75,600. Add £3,000 of business costs you would not otherwise carry, and you need £78,600 of billings across 230 days: about £342 a day.

That number is usually lower than people expect, which is the point. A £400 day rate is genuinely better than £65,000 salaried, but not by the margin the headline comparison suggests.

Worked example: £400 a day

A £400 day rate, billing 46 weeks at five days a week, with £3,000 of annual business costs.

Billable days: 230. Gross billings: £92,000. Less costs: £89,000 of income before tax.

Against a permanent role, that £89,000 has to cover the pension you no longer receive, the holiday you no longer get paid for, and the sick pay you no longer have. Working backwards, £89,000 of contractor income is broadly comparable to a salary in the region of £73,000 to £76,000 once those are valued — still considerably better than £65,000, but not the £92,000 the headline suggests.

Now drop to 42 billable weeks, which is one longer gap between contracts. Billings fall to £84,000 and income to £81,000 — an £8,000 swing from four weeks. That is why utilisation, not rate, is the number contractors should watch.

What this calculation deliberately excludes

Tax treatment is the largest omission and it is deliberate. How a contractor is taxed depends on whether the engagement is inside or outside IR35, whether you operate through a limited company or an umbrella, and on rules that change. The difference between an inside-IR35 engagement through an umbrella and an outside-IR35 engagement through a limited company can be very large on the same headline rate, and no generic calculator should pretend otherwise.

That has a practical consequence worth stating plainly: two contracts at the same day rate can be worth materially different amounts, and the determination is made by the client rather than by you. When comparing offers, the status determination matters as much as the rate.

Risk is the other unpriced element. A contractor carries the risk of not finding the next contract, of a client paying late, and of having no income during illness. Some of that can be insured and some cannot. The premium a rate should carry for that risk is a personal judgement rather than a calculation.

Against that, contracting genuinely buys flexibility, faster skill development across varied environments, and — for many people — a higher ceiling. The arithmetic here is meant to make the trade visible, not to argue either way.

Assumptions and limitations

• Ignores tax entirely — employment and self-employment are taxed very differently
• Takes no view on IR35 status, which can change the net outcome of the same rate substantially
• Billable days are an assumption; the answer is highly sensitive to it
• Values paid leave at salary rate and employer pension at the stated percentage; other benefits are excluded
• Does not price the risk of gaps between contracts or of illness without sick pay
• Not financial advice — take proper advice on structure and status before contracting

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