Tax Calculator
Calculate tax amounts from a subtotal or reverse-calculate pre-tax amounts from a total. Supports multiple tax rates. Free, no signup required.
Enter the subtotal to calculate how much tax to add.
Tax Calculation
Summary
$0.00 + 10% tax = $0.00
Effective tax rate: 0.00%
How to Use Tax Calculator
- 1
Choose a mode
Select 'Add Tax' to calculate tax on a subtotal, or 'Reverse Tax' to extract tax from a total that already includes it.
- 2
Enter the amount
Type the subtotal (in Add Tax mode) or the tax-inclusive total (in Reverse Tax mode).
- 3
Set tax rates
Enter one or more tax rates. Click '+ Add Rate' to add additional taxes like state and local rates.
- 4
Read the results
The calculator shows the breakdown per tax rate, total tax amount, and final total in real time.
Frequently Asked Questions
Related Tools
How Sales Tax Calculation Actually Works
Sales tax seems simple — multiply by a percentage — but the details trip up even experienced accountants. "Forward" tax adds a percentage to a known subtotal: $100 at 8% tax = $108. "Reverse" tax extracts the tax from a total that already includes it: $108 ÷ 1.08 = $100 subtotal + $8 tax. The reverse calculation is not simply $108 × 0.08 (which gives $8.64, an incorrect result), and this mistake appears on countless invoices.
Stacking Multiple Tax Rates
In the US, sales tax often stacks: a state rate (e.g., 6%) plus a county rate (1%) plus a city rate (1.5%) for a combined 8.5%. These are additive — you apply the combined rate once, not sequentially. This differs from countries like Canada where GST and PST may apply independently to the same base, or India where CGST and SGST each apply separately. This calculator adds rates together, which matches US-style combined taxation.
VAT vs. Sales Tax
Sales tax is collected only at the point of final sale. VAT (Value Added Tax) is collected at every stage of the supply chain, with each business paying tax only on the value they add. The math for a single transaction is identical, but VAT creates a chain of input/output tax credits that sales tax does not. If you operate internationally, the distinction affects how you recover tax paid on business purchases.
Rounding and Penny Differences
Tax authorities have specific rounding rules. Most US jurisdictions round to the nearest cent using standard rounding (0.5 rounds up). The EU typically rounds per line item, not on the invoice total. When you have many line items, the order of rounding — per item vs. on the subtotal — can create 1–2 cent differences that trigger reconciliation errors in automated accounting systems.
When to Use a Reverse Tax Calculation
Reverse tax comes up more often than most people expect. Retailers who advertise tax-inclusive prices need to report the tax portion separately for remittance. Accountants reconciling bank deposits against POS totals need the pre-tax figure. Businesses purchasing goods for resale need to extract recoverable input tax from supplier invoices. In all these cases, working backward from the gross amount is the correct approach — not applying the tax rate to the total.
This calculator is for informational purposes. Tax rules vary by jurisdiction. Consult a tax professional for compliance guidance specific to your situation.