What This Tool Does
This sales tax calculator computes the exact tax amount for any purchase using separate state and local rates, then outputs the subtotal, tax, and total in both add-tax and reverse-tax modes. It includes 20 pre-loaded US state averages and supports custom rate entry — making it the only calculator most users need for both consumer purchases and business invoicing.
How to Get Accurate Results
- Use "Remove Tax" mode for receipts. If you have a total and need the pre-tax price, the reverse formula divides by (1 + rate) — not simply subtracting the percentage, which produces an incorrect result.
- Enter your exact local rate, not the state preset. State averages can differ by 1-2% from your city's actual combined rate. Check your county assessor or state revenue department for the precise number.
- Toggle the detailed breakdown to verify the state vs. local split. This is critical for businesses that must remit state and local portions to different agencies.
Methodology
In "Add Tax" mode, the formula is Tax = Price × (stateRate + localRate) / 100 and Total = Price + Tax. In "Remove Tax" mode, the pre-tax price is derived as Subtotal = Total ÷ (1 + combinedRate / 100), then tax is the difference. State and local portions are computed independently against the subtotal so each jurisdiction's share is mathematically isolated. All results are rounded to the nearest cent using standard banker's rounding. The presets use average combined rates sourced from the Tax Foundation's annual state-local data, but actual rates vary by municipality and special taxing district.
Real-World Application
E-commerce businesses use this calculator to verify Shopify and Stripe tax calculations before filing quarterly sales tax returns. By cross-checking the state-local split on high-value transactions, they catch rounding discrepancies that would otherwise compound into audit flags across thousands of orders.
Frequently Asked Questions
How do I calculate sales tax?
To calculate sales tax, multiply the purchase price by the tax rate (as a decimal). For example, with a 7% tax rate: $100 × 0.07 = $7.00 tax. Add the tax to the original price for the total: $100 + $7 = $107. Use our calculator for instant results.
What is the sales tax formula?
The sales tax formula is: Sales Tax = Price × Tax Rate. To find the total with tax: Total = Price × (1 + Tax Rate). To remove tax from a total: Original Price = Total ÷ (1 + Tax Rate). Our calculator handles both adding and removing tax automatically.
How do I calculate reverse sales tax?
Reverse sales tax calculation finds the pre-tax price when you know the total. Formula: Pre-tax Price = Total ÷ (1 + Tax Rate). For a $107 total with 7% tax: $107 ÷ 1.07 = $100. The tax amount is $107 - $100 = $7. Use "Remove Tax" mode for automatic reverse calculations.
What states have the highest sales tax rates?
States with the highest combined state and local sales tax rates include California (9.75%), Tennessee (9.75%), Washington (9.6%), Arkansas (9.5%), and Alabama (9.2%). However, rates vary by city and county. Always check local rates for accurate calculations.
Do all states have sales tax?
No, five states have no statewide sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon. However, Alaska allows local sales taxes. The remaining 45 states plus Washington D.C. charge state sales tax, with additional local taxes in many jurisdictions.
What is the difference between state and local sales tax?
State sales tax is set by the state government and applies statewide. Local sales tax is additional tax imposed by counties, cities, or special districts. The combined rate is what you actually pay. For example, California has 7.25% state tax plus up to 2.5% local tax.
Can I use this calculator for business or personal use?
Yes, this calculator works for both personal and business use. Calculate tax on purchases, estimate project costs with tax included, verify receipts, price products for sale, or calculate tax obligations for bookkeeping. It handles any amount and any tax rate.
Is this sales tax calculator free?
Yes, this sales tax calculator is 100% free with no sign-up, registration, limits, or hidden fees. Calculate sales tax instantly for any location with complete privacy. All calculations happen in your browser.
About the Creator
Tool developed by Tyler, founder of ToolVault. Building professional-grade web utilities since 2025 to help creators and business owners make data-driven decisions. This tool is designed for private, browser-based accuracy.