Coin Bill Inventory Calculator

That ratio approximates how vending machines typically dispense change in practice — quarters dominate because they're the largest common coin and minimize the number of coins needed per transaction, while dimes and nickels fill in smaller remainders. It's a fixed assumption baked into the engine, not something you can adjust per machine, so a route with unusual pricing (lots of exact-quarter items, say) may need a different real-world mix than the calculator suggests.

The model assumes customers tend to pay with round bills regardless of price, so a $1.75 item paid with a $5 bill returns $3.25 in change, while a pricier item is more often paid with something closer to exact value, averaging out to a smaller $1.50 in change. This split is meant to capture that cheap items paid with larger bills generate disproportionately more change to carry.

It pads the calculated change fund per machine above the bare minimum the math says you need, giving you headroom for days with heavier cash traffic than average or an unlucky run of large-bill payments. A 15-25% buffer is typical; setting it to 0% means the fund is sized exactly to the modeled average, with no cushion if a collection cycle runs a bit hot.

Multiplying several floating-point numbers together (daily change, collection days, buffer percentage, machine count) can leave a conceptually exact dollar total like $198 sitting as $198.00000000000003 due to normal floating-point arithmetic. Rounding to the nearest cent first strips that tiny noise out before the final ceiling is applied, so a clean total doesn't get bumped up an extra unneeded dollar.