10 Free Calculators Every UK Freelancer Should Bookmark

Running your own business means doing your own maths. Day rates, tax estimates, late payment interest, cash flow gaps — it's relentless. I built these tools because I got tired of searching for them. They're all free, work in your browser, and don't require an account. The Toolkit 1. Day Rate Calculator Work out what you should charge per day based on your target annual income, working days, tax, and profit margin. Try it free → 2. Self-Employed Tax Calculator 2025/26 Full breakdown of Income Tax, Class 2 and 4 NI, student loan, and take-home pay. Estimate your tax → 3. Late Payment Interest Calculator Calculate statutory interest and compensation under the Late Payment of Commercial Debts Act 1998. Most freelancers don't know they can charge this. Calculate what you're owed → 4. Cash Flow Forecast Plan income vs expenses month by month. Spot cash gaps before they happen. Export to CSV. Build your forecast → 5. Business Expense Tracker Track expenses by HMRC category. Spending breakdow