Add the tax, orback it out of the total.
One field, two directions. Tell it whether your number is the pre-tax price or the tax-inclusive total, and it splits the figure into base and tax cleanly — so your invoices, quotes, and bookkeeping stop disagreeing with each other.
Your numbers
In 'add' mode this is the pre-tax price. In 'extract' mode it's the tax-inclusive total.
Combined sales tax or VAT rate that applies to the sale.
The verdict
Tax amount
$7.50
Total with tax
$108
Pre-tax amount
$100
Effective tax rate
7.5%
A check figure — this should equal the rate you entered.
How the total splits
Sensitivity · tax at different rates
What the tax becomes as the rate moves
| Tax rate | Tax | Total |
|---|---|---|
| 5% | $5.00 | $105 |
| 7.5% | $7.50 | $108 |
| 10% | $10 | $110 |
| 15% | $15 | $115 |
| 20% | $20 | $120 |
In add mode the $100 base is fixed — a higher rate simply stacks more tax on top of it.
Your move
If tax is appearing at checkout, you're losing buyers right there.
Added to $100 at 7.5% → $7.50 tax, $108 total.
A clean tax split is half the job — the other half is where it shows up. Tax that surfaces only on the final step is one of the loudest reasons carts get abandoned and quotes go cold. If your checkout or proposal reveals the all-in number too late, send me your funnel and I'll show you where buyers are dropping and how to surface the real price sooner. Free, and the advice is yours either way.
Plain English
Two questions, one calculator
Sales tax is a percentage added to the price of a sale and collected on behalf of a government. The mechanics are simple — multiply the price by the rate — but the direction matters. Sometimes you know the pre-tax price and need to add tax on top; other times you only have the all-in total and need to pull the tax back out to file it or record clean revenue.
Those are two different sums, and people get them wrong constantly. Backing tax out of a tax-inclusive total is NOT the same as taking the rate off the total. At 10% tax, a $110 total contains $10 of tax, not $11 — because the tax was charged on the $100 base, not on the $110. Subtract the rate from the total and you'll under-report your tax and over-state your net every single time.
This calculator runs both directions. In add mode it takes your pre-tax price and shows the tax and the grand total. In extract mode it treats your number as the tax-inclusive total and divides it back into the true base and the tax it contains. Either way you get the tax amount, the pre-tax base, the total, and the effective rate so you can sanity-check the math.
The formula
Add: tax = price × rate. Extract: base = total ÷ (1 + rate); tax = total − base.
Add 8.5% to a $100 price → tax = $8.50, total = $108.50. Now reverse it: a $108.50 tax-inclusive total ÷ 1.085 = $100 base, leaving $8.50 of tax. Note what you do NOT do: 8.5% of $108.50 is $9.22 — wrong. The tax was levied on the base, so you have to divide, not subtract.
Typical rates, by region
Rates vary wildly by jurisdiction — US sales tax stacks state, county, and city, while VAT is set nationally. Use these as ballparks, then confirm the exact combined rate for the buyer's location before you bill:
| Region | Typical rate |
|---|---|
| US state sales tax | 0-10% |
| UK / EU VAT (standard) | 20% |
| Canada GST/HST | 5-15% |
Source: Tax Foundation state & local sales tax rates, 2025 · 2025
Reading the result
Your invoices show a total but no tax line.
Use extract mode. Treat the charged total as tax-inclusive, pull the tax out, and book the base as revenue and the tax as a liability you owe — not income.
You're quoting a customer a price.
Use add mode so the quote shows the pre-tax price, the tax, and the all-in total separately. Hidden tax at checkout is the fastest way to spike cart abandonment.
The effective rate doesn't match the rate you typed.
It should match exactly in both modes — that field is a sanity check. If it's off, you've rounded the tax or base somewhere upstream; reconcile before filing.
You sell across multiple states or countries.
There is no single rate. Tax is destination-based in most US states and VAT follows the customer's country. Run each jurisdiction separately rather than averaging.
Getting sales tax right
01Tax the base, not the total
When backing tax out, always divide by (1 + rate). Subtracting the rate from a tax-inclusive total under-reports the tax you collected.
02Show tax as a line item
Buyers trust a price that's broken out: base, tax, total. Surprise tax at the final step is a top driver of abandoned checkouts.
03Use the buyer's location
Most US sales tax is destination-based and VAT follows the customer's country. Charge the rate where the goods land, not where you sit.
04Tax is a liability, not revenue
Money you collect as tax isn't income — it's owed to the government. Park it separately so you're never spending your remittance.
05Watch economic nexus
Cross a state's sales or transaction threshold and you must register and collect there, even with no physical presence. Track your interstate sales.
06Keep exemption certificates
Wholesale and resale buyers may be exempt — but only if you hold a valid certificate on file. No paper, no exemption in an audit.
07Round per line, then sum
Rounding the grand total instead of each taxable line can drift by cents over a long invoice. Be consistent with your accounting software.
08Reconcile effective rate
If your booked tax ÷ booked base doesn't equal your stated rate, something rounded wrong. Catch it monthly, not at filing.
The vocabulary
- Sales tax
- A percentage added to a sale at the point of purchase, collected by the seller and remitted to a tax authority.
- VAT
- Value-added tax: a consumption tax used across the EU/UK, typically quoted tax-inclusive in consumer prices.
- Tax-inclusive total
- A price that already contains the tax. Backing the tax out requires dividing by (1 + rate).
- Pre-tax base
- The price of the goods before any tax is applied — the figure tax is calculated on and the amount you book as revenue.
- Effective rate
- Tax ÷ pre-tax base, as a percentage. A check figure that should equal the rate you entered.
- Nexus
- The connection (physical or economic) that obliges a seller to collect and remit tax in a given jurisdiction.
Sales tax questions, straight answers
Multiply the pre-tax price by the tax rate as a decimal. At 8.5% on a $100 price, that's $100 × 0.085 = $8.50 of tax, for a $108.50 total. That's 'add' mode in this calculator.
Keep going
A calculator tells you what. A call tells you what to do about it.
Send me the account behind these numbers. I'll tell you straight where the money's leaking and what I'd fix first — free, and you keep it whether you hire me or not.