Count the cash: add up what is there, and count back the change

How it adds

• One line for each kind of U.S. bill and coin: $100, $50, $20, $10, $5, $2 and $1 bills; dollar coins, half dollars, quarters, dimes, nickels and pennies.
• Each box takes a whole number from 0 to 9,999: how many you have, not what they are worth. An empty box counts as none. A box holding anything else is marked and left out of the sum until it is fixed.
• Every amount is kept in whole cents inside the page, so no cent is lost to rounding.
• It shows four sums: everything, the bills alone, the coins alone, and how many bills and coins you counted, so you can check that against the pile.
• Sort first, then count. The page can only add what you tell it. A miscounted pile gives a wrong sum that looks right.

What it should come to

• Write the amount you expect, up to $999,999.99: the rent, the number on the slip, what the envelope said.
• The page says exactly right, how much over, or how much short.
• Over or short, count again before anything else. Bills stick together, and a coin sits in the wrong pile.
• This page does not know why a count is off, and it does not know what your workplace does about it.

The change, and counting it back

• The change is what was handed over, less the price. If less was handed over than the price, the page says how much more is owed.
• It makes the change from ten pieces: $100, $50, $20, $10, $5 and $1 bills, and quarters, dimes, nickels and pennies. It takes the biggest piece that fits, again and again, which gives the fewest pieces. It does not use $2 bills, half dollars or dollar coins.
• Counting back starts at the price and goes up, smallest pieces first. For $13.42 paid with a twenty: say $13.42; three pennies, $13.45; a nickel, $13.50; two quarters, $14.00; a $1 bill, $15.00; a $5 bill, $20.00. When the last amount you say is what they gave you, the change is right, and nobody had to subtract.
• If you are out of a piece, use smaller ones that come to the same. The amount of change stays the same; only the pieces differ.
• This part stands alone. It does not look at the count above, and does not know what is in your drawer.

What this page does not do

• It does not round. If cash totals are rounded to five cents where you are, this page does not know the rule, and gives the change to the cent.
• It does not know other money than U.S. dollars, and it cannot tell whether a bill is real.
• It does not add tax or a tip. Percent does that; bring the answer here.
• It does not keep anything. If the page is closed or loaded again, the numbers are gone. Write the sum down if you need it later.
• It was tried in one browser only (Chromium).

Every time the page is built, a program checks it three ways. It checks 40 examples worked by hand. Then it makes up 3,000 piles of bills and coins and adds each one again a second way, one piece at a time, and the build stops if the two sums differ. Last, for every amount of change from $0.00 to $300.00, all 30,001 of them, it checks that the pieces come to that amount, that no smaller number of pieces could, and that counting back ends on what was handed over.