The minimum order is 100 gallons or 150 gallons depending on the dealer. We’ve got dealers who are happy to accept orders in multiples of 10. A calculator’s not needed for this part! All you need to do is place your order in multiples of 10 gallons and you’re good to go! If your tank doesn't take the minimum order (hopefully it does) the price may change and there could be an under-delivery fee. If you've ordered too much don’t worry we've got you covered! Your money will go back to the card you paid with.