Most freelance developers pick a day rate by vibes.
"What does everyone else charge? £400? £500? Cool, I will go with that."
Then they work out their actual take-home 6 months later and wonder why they are not saving anything.
Here is the maths nobody tells you.
The £500/day illusion
Let's say you charge £500/day. Sounds great. £2,500/week. £130k/year if you worked every day.
But you don't work every day.
Realistic billable days per year: 200-220 (not 260)
You lose days to:
- Bank holidays (8 days)
- Holiday you actually take (20-25 days)
- Sick days (5-10)
- Admin, invoicing, chasing payments (10-20 days)
- Pipeline gaps between contracts (10-30 days)
- CPD, conferences, networking (5-10 days)
So £500/day × 210 billable days = £105,000 gross.
Still sounds decent. Until the deductions hit.
What actually comes off
| Item | Annual cost |
|---|---|
| Income Tax (sole trader) | ~£27,000 |
| National Insurance (Class 2 + 4) | ~£5,200 |
| Professional insurance | £300-800 |
| Accountant | £300-600 |
| Software/tools | £500-2,000 |
| Home office costs | £500-1,500 |
| Pension (if you bother) | £5,000-10,000 |
| Training/conferences | £500-2,000 |
Conservative total: £35,000-45,000 in deductions.
That £500/day rate? It is actually about £290-340/day take-home. Or roughly £60k-70k net.
Which is fine. But it is not £130k.
The comparison trap
Permies earning £70k get:
- Employer pension contributions (~£5k)
- Paid holiday (25 days = £6.7k)
- Sick pay
- Maternity/paternity pay
- Training budget
- Equipment provided
Total package value: probably £85k+.
So your £500/day rate is roughly equivalent to a £70-75k salary. Not the £130k it looks like on paper.
How to actually calculate your rate
Work backwards from what you need:
- Target net income (what you want in your pocket)
- Add tax + NI (roughly 35-40% for most freelancers)
- Add business costs (insurance, tools, accountant)
- Add pension contributions (because nobody else is doing it for you)
- Divide by realistic billable days (200-220, not 260)
I built a free calculator that does this: landolio.com/tools/day-rate-calculator
Plug in your numbers. The result is usually higher than you expect.
The uncomfortable truth
Most freelance developers are undercharging. Not because the market won't bear higher rates, but because they calculated their rate wrong in the first place.
They divided their target salary by 260 working days, forgot about tax, forgot about the days they won't bill, and ended up working harder for roughly the same money as employment.
Do the maths properly. Then have the awkward conversation with your next client.
I build free tools for UK freelancers — tax calculators, invoice generators, contract builders. All free, no signup.
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