Net amount and VAT percentage—gross price and tax portion (educational; rates vary).
Gross = net × (1 + rate ÷ 100) with net non‑negative and rate between 0 and 100. The “VAT part” line is gross − net. Inclusive/exclusive tax definitions beyond this simple model are not handled.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.