About this tool
Choose the currency precision and whether the entered amount is before or after tax, then review a subtotal-plus-tax reconciliation and formula.
Tax Calculator is helpful when the practical question is whether tax should be added on top or separated from a price that already includes it. It is useful for quoting, invoicing, budgeting, and receipt checks across VAT, GST, and sales-tax style workflows.
- Parses USD, EUR, and GBP to two decimal minor units and KRW to whole units without floating-point amount conversion.
- Uses an exact rate with up to three decimal places and BigInt half-up division for added tax or included-tax subtotal.
- Rejects unsupported query policies and reconciles before-tax amount plus tax to the displayed after-tax total.
How to use Tax Calculator
Choose whether the tax is added on top of the base amount or already included inside the final price, then enter the amount and rate to see subtotal, tax amount, and final total together. Use tax-included mode when you want to reverse-engineer a receipt or advertised price.
When this tool is useful
- Add VAT, GST, or sales tax on top of a pre-tax subtotal.
- Back tax out of a tax-included total on a receipt or quoted price.
- Check invoice math quickly before sending or approving a payment.
Practical tips
- Use tax-included mode when the displayed total already includes tax and you need the base amount underneath it.
- Double-check the tax rate before comparing prices across regions because VAT and sales-tax rules vary.
- Pair this with the percentage calculator if you also need discount or markup math on the same quote.
Examples you can test
Load an example, compare the result with the expected output, then replace it with your own input.
Estimate sales tax
Example input
Subtotal: 120, tax rate: 8.25%
Expected output
Tax amount and total
Useful for quick checkout, invoice, or quote estimates.
Back out pre-tax amount
Example input
Total: 108.25, tax rate: 8.25%
Expected output
Estimated pre-tax subtotal
Reverse calculations are helpful when a receipt only shows the final amount.
Validation checklist
- Confirm the correct tax rate and whether it applies to the full amount.
- Check rounding rules before using totals in invoices or reports.
- Do not use a general tax calculator as legal, accounting, or tax advice.