From net to gross, or from a tax-included price back to net. Any rate.
Net = gross ÷ (1 + rate). At 20%, a 120.00 price is 100.00 net + 20.00 tax. The common mistake is subtracting 20% of the gross (120 − 24 = 96), which understates net by 4.00.
Amounts are shown to two decimals without truncation. Some jurisdictions (Korea, for example) truncate tax to whole currency units on invoices; check your local rule if the cents matter.
Sales tax is added once at the final sale; VAT is charged at each step and reclaimed by businesses. For a single price calculation, the arithmetic is the same.
No. The arithmetic runs in your browser.
The rate that applies where the sale is taxed. Common ones are listed as presets; type any other value.
No. It calculates one rate on one amount.