Sales Tax Calculator

What this calculator does, and how it differs from GST

This calculator handles a flat, single-rate sales tax — the kind commonly charged at checkout in the US, where each state or city sets one rate applied on top of the listed price. It's a different tax structure from India's GST, which uses fixed slabs (5%, 12%, 18%, 28%) baked into the price rather than a locally variable add-on rate. If you need GST specifically, use the GST Calculator instead — this tool is for any flat-percentage sales tax.

The formulas

• Adding tax to a pre-tax price: tax = price × (rate ÷ 100); total = price + tax
• Extracting tax from a tax-included total: pre-tax price = total ÷ (1 + rate ÷ 100); tax = total − pre-tax price

Worked example

A $100 item with a 7% sales tax: tax = 100 × 0.07 = $7, so the total at checkout is $107. If instead you only know the final receipt total was $107 and want to back out the pre-tax price: $107 ÷ 1.07 = $100 — confirming the same numbers work in reverse.

Common mistakes

• Applying the tax rate to a tax-included total the same way as a pre-tax price — dividing by (1 + rate) is not the same as multiplying by (1 − rate), and using the wrong one gives a slightly wrong answer.
• Assuming one flat national rate — in reality, sales tax rates vary by state, county and even city, so always use the actual local rate.

Limitations

This calculator applies a single flat rate you enter — it doesn't know local tax rates, tax-exempt categories, or combined state+local rate stacking, all of which vary by jurisdiction. Enter the actual combined rate that applies to your purchase for an accurate result.

Frequently asked questions