Quoting a customer, checking an online cart or filling in an invoice all come down to the same sequence: price times quantity, minus any discount, plus shipping and sales tax. The order of those steps changes the result, so this calculator applies them the way most US retailers and invoicing systems do and shows each line of the calculation.
How to use the sales calculator
- Enter the unit price and quantity.
- Enter a discount as a percentage or a dollar amount off the whole order (leave it blank for none).
- Add shipping or delivery charges, if any.
- Enter the sales tax rate and tick shipping is taxable if your state taxes delivery.
- Read the order total on the tape, with each component and the effective price per unit. The table repeats the calculation for other quantities.
Order total formulas
Each money amount is rounded to the cent before the next step, which matches how invoices are printed.
Worked example
A customer orders 3 items at $24.99 with a 10% promotional discount, $5.95 shipping and 8.25% sales tax. Shipping is not taxable in this state.
Subtotal = 3 × 24.99 = $74.97
Discount = 74.97 × 10% = $7.497 → $7.50, leaving $67.47
Sales tax = 67.47 × 8.25% = $5.566 → $5.57
Total = 67.47 + 5.95 + 5.57 = $78.99, or $26.33 per item
If the state taxed shipping, the tax would be calculated on $73.42 instead, giving $6.06 and a total of $79.48.
How the order of steps changes the total
| Approach | Tax base | Tax | Total |
|---|---|---|---|
| Discount before tax (standard) | $67.47 | $5.57 | $78.99 |
| Tax before discount | $74.97 | $6.19 | $79.61 |
| Discount before tax, shipping taxable | $73.42 | $6.06 | $79.48 |
Applying the discount first is the norm for store discounts and promotions; some states compute tax on the pre-coupon price for manufacturer coupons because the retailer is reimbursed for the difference.
Tips for quotes and invoices
- Dollar discounts on bulk orders behave differently from percentages: $10 off is 13% on a $75 order but only 1% on $1,000. Compare both with the quantity table.
- Round per line or per invoice. Most systems calculate tax once on the invoice total. Calculating it per line and adding can differ by a cent or two.
- Exempt customers. Resellers and nonprofits may present exemption certificates; set the tax rate to 0 for those orders.
- Know your rate. The state sales tax calculator has every state’s base rate and the average local rate.
For a single-item tax check, the sales tax calculator is quicker, and the discount calculator handles stacked coupons. To see what the order earns you after costs, use the profit calculator.
Results are estimates. Taxability of shipping, coupons and specific products varies by state; check your state revenue department's rules.
Frequently asked questions
In what order are discounts, shipping and tax applied?
Normally the discount comes off the merchandise subtotal first, then sales tax is calculated on the discounted amount, and shipping is added. Whether shipping itself is taxed depends on the state and on how the charge is presented.
Is shipping taxable?
It depends on the state. Some states tax delivery charges whenever the item is taxable, others exempt shipping that is listed separately on the invoice, and a few tax it only in certain cases. Tick the shipping-is-taxable box if your state taxes it.
Why does the discount show $7.50 instead of $7.497?
Money amounts are rounded to the cent at each step, as a cash register or invoicing system would. 10% of $74.97 is $7.497, which rounds to $7.50.
What is the effective price per unit?
It is the final total, including discount, shipping and tax, divided by the quantity. It is useful for comparing offers with different shipping charges or bulk discounts.