Stacked discounts
Two discounts are applied one after the other, not added together. 20% off and then an extra 10% off is 0.8 × 0.9 = 0.72 of the price, so you save 28%, not 30%. Fill in the extra discount box and the calculator shows the combined discount. A coupon for a fixed amount is taken off after the percentage discounts, and sales tax is added last.
Tip and split
Enter the bill, a tip percentage and the number of people. To keep things simple you can round each share up, for example to the next dollar; the page shows how much extra that collects, or how to have everyone pay a round amount with one person covering the rest.
Which pack is cheaper?
On the Unit price tab enter the price and size of each option, and the number of pieces if a pack holds several. The cheapest per unit is highlighted and the others show how much more they cost, both per unit and per 100 units, which is handy for grams and millilitres.
Is anything sent to a server?
No. Everything runs in your browser. Nothing you enter is uploaded; settings you change are only remembered on this device.