# Tax, Discount & Percentage Calculator Calculate tax-exclusive to tax-inclusive, tax-inclusive back to tax-exclusive, or the tax alone, at 10%, 8% or any rate you enter. Choose how to round below one unit, and see the formula used for each result. - URL: https://tools.itlibra.com/en/tax-percent-calculator - On-device・No upload - Last updated: 2026-10-23 ## How to use 1. In the “Sales tax” tab, choose whether you start from the price before tax or the price with tax, then enter the amount. The rate can be 10%, 8% or any value you type. 2. Choose round down, round half up or round up for the part below one unit. The results and the formula change together, so check which rule your business uses. 3. For items at 10% and 8% on one bill, enter each amount and rate in “Mixed rates on one bill”. Lines at the same rate are added first, then rounded once. 4. The “Discount” tab works out % off, amount off, two-step discounts and the price with tax after a discount. In a two-step discount, step 2 applies to the result of step 1. 5. The “Percentage” tab works out what % A is of B, B% of A, the change rate (A to B) and the percentage-point difference. Results appear as you type; there is no button to press. 6. Copy any result on its own, or use “Copy all results” to copy the formulas with them. ## Use cases - Set a shelf price with tax from a price before tax - Work out the price before tax and the tax included from a receipt or invoice total - Check a bill that mixes 8% food and 10% goods - Check how much a 20% discount followed by 10% off comes to in total - Get a quick year-on-year change rate or a share of survey answers - Decide whether to say a change from 3% to 5% is a rise of 2 points or about 66.7% ## What it does ### Reverse tax calculation to the yen To get the price before tax from the price with tax, the tax is worked out first (price × 10 ÷ 110), then taken away, as the National Tax Agency describes. For 109 yen, rounding down gives tax 9 and a price before tax of 100; rounding half up gives tax 10 and 99. The rule is set by your business; the tool shows both. ### Mixed rates are rounded once per rate For invoices, the National Tax Agency asks for one rounding per tax rate (Q57). Lines at 10% and 8% are added within their rate first; the tool does not round each line and add the results. ### Two-step discounts show 28% Taking 10% off a price already reduced by 20% gives 28% off in total, not 30% (0.8 × 0.9 = 0.72). Step 1 is rounded to the yen before step 2 is applied, so the amounts you see match. ### Formula shown for every result Each result shows the formula and the intermediate values, such as “1,000 × 10% = 100 (round down)”, so you can check which numbers were used. ### Share and change kept apart A is what % of B, B% of A, the change rate and the percentage-point difference are each calculated separately. A move from 3% to 5% is about a 66.7% rise, or a 2-point rise. ## Capability matrix | Feature | Support | Notes | | --- | --- | --- | | Before tax → with tax, with tax → before tax (reverse), tax only (added and included) | Supported | — | | Tax rates 10%, 8% or any value from 0 to 100% (up to three decimals) | Supported | — | | Rounding: round down, round half up, round up | Supported | Choose the rule your business uses | | Totals for one bill with mixed rates (one rounding per rate) | Supported | Up to 10 lines | | % off, amount off, two-step discounts and the price with tax after a discount | Supported | — | | A is what % of B, B% of A, change rate and percentage-point difference | Supported | — | | Issuing invoices, checking registration numbers | Not supported | This tool does not create invoices | | Deciding which items are at the reduced 8% rate | Not supported | Check the National Tax Agency guidance | | Other countries’ VAT or GST exemptions, credits and tax categories | Partial | Any rate can be typed, but the rules of each system are not applied | | Currency conversion, loan interest and compound growth | Not supported | Not covered on this page | ## Limits & notes - Amounts (before tax, with tax, price, amount off) are whole units, up to 15 digits. Percentage inputs take up to six decimals; tax and discount rates take up to three. - Rates run from 0 to 100%. 10% and 8% are the starting values; for rates that change under a new rule, check the latest National Tax Agency guidance. - Percentage and change-rate results are rounded to six decimal places for display. - Negative amounts are not accepted. Percentages, change rates and point differences can be negative. - Mixed-rate bills take up to 10 lines. Phones can run the calculations, but comparing several results is easier on a PC. ## Privacy & safety Amounts and rates you enter are calculated in your browser only. Nothing is sent to or stored on a server, and the inputs are not put in the URL. ## FAQ ### How is the consumption tax calculated from a price that includes tax? Multiply the price with tax by 10 and divide by 110 (for 8%, multiply by 8 and divide by 108). For 1,100 yen, 1,100 × 10 ÷ 110 = 100 yen is the tax. The price before tax is the price with tax minus that tax. ### What is 1,000 yen plus 10% tax? 1,000 × 10% = 100 yen of tax is added, so the price with tax is 1,100 yen. At 8% it is 1,080 yen. ### Is the price before tax of 109 yen 99 or 100? It depends on rounding. The tax 109 × 10 ÷ 110 = 9.909… is 9 when rounded down, so the price before tax is 100; rounded half up or up, the tax is 10 and the price before tax is 99. Use the rule your business follows. ### What is the total discount for 20% off and then 10% off? It is 28% off in total: 0.8 × 0.9 = 0.72, so 72% is left. It is not 30%, because the second discount applies to the price after the first. ### What is the difference between a change rate and percentage points? A change rate is how much a value rose or fell as a percentage of the original. Percentage points are the difference between two percentages. If a share goes from 3% to 5%, that is 2 points, and the change rate is about 66.7%. ### How do I work out the tax on a bill with both 10% and 8% items? Add up the amounts at each rate, then round the tax once for each rate. The National Tax Agency sets one rounding per tax rate on invoices as the rule (Q57). Use the “Mixed rates on one bill” section to calculate it.