UK business calculators
Twelve calculators built for UK freelancers, contractors and limited company directors — sole trader vs Ltd, salary vs dividend, IR35, VAT, day rate — with AI explanations of the trade-offs.
All business calculators
From going freelance to optimising your Ltd company — every UK self-employment decision in one place.
Salary vs dividend
Optimal director pay split with AI breakdown
Sole trader vs Ltd
Take-home compared at any income level
IR35 inside vs outside
PAYE vs Ltd take-home on the same contract
Limited company profit
Post-Corporation Tax distributable profit
Flat Rate VAT Scheme
FRS vs standard scheme by your sector rate
Freelancer day rate
Rate needed to hit target net income after costs
VAT threshold
Rolling 12-month turnover check
Director’s loan account
S455 charge, BIK and write-off rules
Director pension contribution
Employer contribution from Ltd company
Mileage allowance
AMAP 45p/25p rates for business mileage
Sole trader Class 2/4 NI
National Insurance on self-employed profit
Cash runway
Months to zero at current burn rate
About business calculators on Calclens
Calclens builds UK business and freelance calculators that go one step further than the rest of the web — every result comes with a plain-English AI explanation, generated on demand. The calculation runs instantly in your browser. The AI layer is optional.
UK self-employment is a structure game. Sole trader vs limited company, salary vs dividend, inside IR35 vs outside, Flat Rate VAT vs standard, employer pension contribution vs personal — each choice changes how much tax you pay and what you actually take home. Generic global calculators don’t model any of this. Ours treat it as the central question.
What makes these business calculators different
- Structure-aware comparisons — sole trader and Ltd company tax engines run side by side, IR35 inside vs outside on the same contract, Flat Rate VAT vs standard for your sector
- Director optimisation — the salary vs dividend calculator finds the actual optimal split, not a rule of thumb
- The traps HMRC waits for — director’s loan account S455 charge, mileage allowance limits, Class 2 small profits threshold, VAT registration timing
- Honest day-rate maths — the freelancer day rate calculator accounts for holiday, sick days, pension, and the gap between gross billings and what lands in your account
- AI explanation layer — powered by Claude (Anthropic), explained on the how AI works page
- Free forever — no sign-up, no accounts, no display ads, no affiliate links to accountants or umbrella companies
- Built in public — sources from HMRC and FCA-referenced material, documented on our methodology page
Which business calculator should I use?
Should I go limited or stay sole trader?
The sole trader vs Ltd calculator compares both structures at your income level. Below roughly £30k profit, sole trader usually wins after accountant costs. Above £50k, Ltd is usually better for take-home but adds admin and filing requirements. The calculator shows the exact break-even for your numbers.
I’m a Ltd director. What salary and dividend should I take?
The salary vs dividend calculator finds the optimal split for your situation. Typically you’d pay yourself a small salary up to the secondary NI threshold to claim Corporation Tax relief without triggering employer NI, then take the rest as dividends. The calculator confirms the exact numbers based on current bands.
This contract is inside IR35. How much worse off am I?
The IR35 inside vs outside calculator runs the same day rate through both treatments. Inside IR35 you’re effectively PAYE with no expenses; outside you can run it through a Ltd company and pay yourself in salary plus dividends. The difference on a typical contract is often 15-25% of take-home.
Am I going to hit the VAT threshold?
The VAT threshold calculator tracks your rolling 12-month turnover — that’s how HMRC measures it, not your tax year. You must register within 30 days of going over. If you’re close, the Flat Rate VAT calculator shows whether the FRS scheme saves you money once you do register.
What day rate should I charge as a freelancer?
The freelancer day rate calculator works backwards from the net income you want. It accounts for holiday, sick days, business expenses, pension and tax, then tells you the gross day rate to charge. Most early freelancers underprice because they forget unbillable days.
I took money out of my company as a loan. What now?
If you borrowed from your Ltd and haven’t repaid within nine months of the year end, HMRC charges 33.75% S455 on the outstanding balance (refundable once you repay). The director’s loan account calculator shows your S455 liability and the benefit-in-kind tax if the loan was interest-free above £10k.
Are these figures financial advice?
No. The calculators give you working numbers based on current HMRC rules. The AI explanation provides context, not regulated advice. For a binding decision — incorporating, IR35 contract review, or VAT scheme choice — speak to a chartered accountant or specialist tax adviser.