Coupons, discounts, sales–they all seem to conspire to keep you from knowing exactly what something costs. Throw in sales taxes that vary from one jurisdiction to the next, and you may be tempted to just give the sales clerk your charge card and try not to think about it.

This handy tool can be your solution. Just enter the original cost, the tax rate, and one or two discounts (in percentages or dollar amounts). Discount Calculator instantly figures your final cost, and tallies the amount and percentage of your savings as well.

Built-in plus and minus buttons let you adjust any entry quickly without a keypad. If you’re doing most of your shopping under a single tax rate, a default rate can be set.