When measuring for a new bathtub, there are several measurements that you need to take into account:
Overall Length: The tub’s overall length measures the longest part of the tub, including the lip or shelf of the tub.
Overall Width: The tub’s overall width measures the widest part of the tub. For tubs with varying widths (like an oval-shaped tub), this measures the tub where it is at its widest, usually at the center.
Overall Height: The tub’s overall height measures the tub’s height from the floor to the tub’s rim. For freestanding clawfoot tubs, the overall height should include the height of the clawfoot base legs.
Basin Length: Unlike the overall length, the tub’s basin length measures the longest part of the tub’s basin or inside the tub. Many tub basins are angled to provide better lumbar support. For this reason, your basin length may be shorter at the bottom but longer near the top of the basin. Most basin length measurements refer to the length of the bottom of the basin, but specification sheets will include two separate measurements; one for the top basin length and one for the bottom basin length.
Basin Width: The tub’s basin width measures the tub’s inner basin at its widest point, which is usually found at the center of the tub.
Soaking Depth: The soaking depth measures from the bottom of the basin to the slotted overflow on the side of the tub. It measures how high the water can reach in your tub before reaching capacity. This is different from the basin depth, which measures from the bottom of the basin to the lip or top of the tub.
Weight & Basin Capacity: Though sometimes overlooked, the tub’s weight and basin capacity is crucial to a successful installation. The basin capacity measures how many gallons the tub can hold. The weight is the weight of the tub before adding water. Put together, the weight and the added weight of the water capacity will determine whether you need to reinforce your floor or not.
When browsing for a new tub, most measurements in the product titles refer to the overall length x overall width x overall height, like so:
Kohler Ceric 64.94" x 31.13" x 22.88" Freestanding Bathtub in White
However, some tubs simply go by the overall length:
Duravit Starck 70.88" Acrylic Freestanding Bathtub in White
Regardless, always check both the product details and the attached specification sheets for tub measurements before purchasing a new tub.