Why DuckCoupon builds free tools
DuckCoupon has long been the UK's home for verified discount codes and voucher listings. Over time we noticed the same handful of small but essential calculations coming up again and again: working VAT out of an invoice, deciding whether eBay or Vinted is the cheaper place to list a pre-loved jacket, splitting a bill, or estimating postage. The kind of maths that should not require an account, an email address, or a credit card.
Every tool on this page runs entirely in your browser. The numbers never leave your device, there are no analytics tied to the inputs, and you can use them as many times as you like for free. We add a new tool whenever we spot a calculation that UK shoppers and sellers are quietly doing by hand — and we publish each one as a permanent, searchable page that explains the underlying rules (for example, what counts as a reduced-rate VAT supply, or when eBay waives its Final Value Fee).
If you have a tool suggestion — a calculator, an estimator, a comparison widget — let us know via the contact page. The most-requested ideas get built next.