Home / Free tools / Combined Sales Tax Rate Stacker
Free tool

Combined Sales Tax Rate Stacker

Stacks state, county, city and special district rates into one combined rate and shows the tax and checkout total for any order, or backs the tax out of a tax-included total.

Your numbers

Results update as you type.

Your estimate

Combined sales tax rate...
Pre-tax price...
Sales tax...
Total charged...

Estimates only. Assumptions are listed below, and you can change every input.

A single US ZIP code can carry four layers of sales tax: the state rate, a county rate, a city rate and one or more special district rates for transit, stadiums or improvement zones. Sellers who charge only the state rate under-collect, and sellers who guess at a combined figure often over-collect. Receipts also sometimes show a tax-included total with no breakdown, which makes it hard to record the pre-tax sale correctly.

This calculator adds the rates you enter into one combined percentage and applies it to an order amount. In add mode, the amount you enter is the pre-tax subtotal and the tool returns the tax and the total to charge. In back-out mode, the amount is the total already paid and the tool divides by one plus the combined rate to recover the pre-tax price and the tax portion. Results are rounded to the cent.

How to use this tool

  1. Look up the state, county, city and special district rates for the delivery address and enter each one.
  2. Enter the order amount and choose add mode for a pre-tax subtotal or back-out mode for a receipt total that already includes tax.
  3. Use the combined rate to check your checkout settings and the tax amount to reconcile your records.

What the math assumes

  • Assumes all four rate layers apply to the full order amount and are simply added together, which is how most US jurisdictions stack rates.
  • Assumes the entire order is taxable; it does not separate exempt items, shipping or discounts.
  • Assumes the rates you enter are current for the delivery address; the tool does not look up rates for you.
  • Rounds tax and totals to the nearest cent, which can differ by a cent from a platform that rounds each line item separately.

Frequently asked questions

Why does my combined rate differ from the rate my checkout charged?

Common causes are a special district you did not include, a rate change that took effect recently, or your platform using origin-based sourcing while you looked up the destination rate. Compare each layer separately to find the gap.

How do I back out sales tax from a total?

Divide the total by one plus the combined rate expressed as a decimal. For example, a $108.25 total at 8.25% becomes $108.25 divided by 1.0825, which is $100.00 pre-tax and $8.25 tax. Back-out mode does this for you.

Are rates always stacked by simple addition?

For nearly all US jurisdictions, yes: the combined rate is the sum of the state and local layers. A few places cap the local portion or apply a different rate to certain products, so treat the result as the general merchandise rate.

Link to this toolhttps://salestaxly.com/tools/combined-rate-stacker/

Free for readers and publishers alike. If you cite the result in an article, a link to this page helps others find it.

More free tools from SalesTaxly

  • Economic Nexus Threshold Tracker: Estimates how close your online store is to a state's economic nexus threshold and when you will cross it at your current sales pace.
  • Sales Tax Filing Workload Calculator: Estimates how many sales tax returns your store files each year, the hours and cost that takes by hand, and the net savings if you automate.

Charge the right US sales tax, every time

US sales tax rates and lookup for online stores.

Look up a rate