A standard bathtub holds 24 gallons of water when filled to the rim. Larger tubs hold up to 110 gallons of water when filled all the way.
Bathtubs are available in a variety of sizes. To determine the amount of water a tub can hold, multiply the tub's width measurement by its length. Take this result, and multiply by the depth measurement of the tub. Take this result, and divide by 1,728 for the number of cubic feet of water the tub can hold. Multiply this result by 7.5 to obtain the number of gallons of water the tub can hold.