How do I measure the soaking depth of a bathtub?

To measure the soaking depth of a walk-in bathtub, run a tape measure from the top of the seat straight up to the center of the overflow opening, because the water can never rise above the overflow. Then record the length of the seat and the interior length of the tub, since those two figures decide how you sit in that water. The definition behind the number is in What Is Soaking Depth on a Walk-In Tub?; this page shows how to take the measurements yourself on a seated walk-in tub, a lay-down tub or a standard bathtub, and how to compare them with your own body.

Why You Measure to the Overflow and Not the Rim

On every Ella tub the published depth is measured to the overflow. Water rises to the overflow opening and then runs out, so the height of the tub wall tells you nothing about how deep you will sit. Measuring to the rim is the most common mistake, and it produces a figure you can never fill to. The rule at bath time is the same rule you use with the tape: fill no higher than the center of the drain handle, and remember that the overflow carries away anything that rises above it. Both videos on this page show the three factors that set soaking depth on a seated tub: a measurement from the top of the seat to the center of the overflow, the length of the seat, and the interior length of the tub.

Measuring a Walk-In Tub with a Seat, Step by Step

1. Find the overflow. It is the opening in the tub wall on the drain side, near the drain handle, and it is the point the water level stops at.
2. Hold the end of the tape flat on the top surface of the seat and measure straight up to the center of the overflow opening. This is the seat-to-overflow depth, the figure the spec sheets quote as soaking depth.
3. Measure the seat length from its front edge to the backrest. A shorter seat lets you settle lower; a longer seat holds you more upright.
4. Measure the interior length of the tub from end to end inside the shell. More legroom lets you stretch out and sink lower into the water.
5. While you have the tape out, measure the seat width, because the seat must be wider than your seated hips.

Write all four numbers down together. Soaking depth is not one figure; the seat-to-overflow measurement caps the water, and the seat length and interior length decide how your body sits in it.

Measuring a Lay-Down Tub or a Standard Bathtub

A tub with no seat is measured from the floor of the tub to the overflow. On the LayDown 30x60 that figure is 15 3/4 inches, and the team has confirmed the water does reach 15 3/4 inches. The LayDown floor is a flat 46 by 20 inches, and the soaking space widens to about 53 by 25 1/2 inches above the floor, inside a tub that is 30 inches wide, 60 inches long and 21 inches tall. Ignore the seat line printed on the LayDown spec sheet; it uses the same template as the seated tubs even though LayDown tubs have no seat. A standard bathtub measured the same way, floor to overflow, gives about 11 inches, compared with the 15 inch soaking depth of a LayDown, which is the difference you feel when you recline. The exterior sizes to check against your alcove are in Walk-In Tub and Shower Base Sizes and How to Measure for Fit.

Measuring Yourself so the Number Means Something

There is no soaking depth calculator, because your own size decides the result. A taller bather sits higher in the water than a shorter one on the same seat, and a long torso feels a shallower soak than a short one. The reliable method is to sit in a chair facing a wall, in a relaxed position, and take these measurements:

• Your hips while seated. The tub seat must be wider than this number.
• Your shoulder width while seated, to make sure the tub has the proper shoulder room.
• Your length from head to feet while seated, to compare with the interior length of the tub.
• Your seated torso, from the seat surface to your shoulders, to compare with the seat-to-overflow figure.

Seat widths across the Ella lineup run from 19 inches on the Petite and Transfer26 to 29 inches on the TransferXXL, so the hip measurement rules tubs in or out quickly. For bathers around six feet and taller, What size walk-in tub fits a six-foot-tall person? explains why the long-seat models suit them and why the same length is a poor fit for a shorter partner. Fit, not weight, is also what decides whether a tub holds you, as What Is the Total Weight Capacity of a Walk-In Tub? explains.

Published Figures to Check Your Tape Against

Across the mid-size models the seat-to-overflow figure runs roughly 15 to 18 inches, and the Deluxe and Big4One sit above that range. If your tape gives a different number on a tub you already own, the first thing to check is what you measured from: the seat surface on a seated tub, the floor on a lay-down tub, and always to the center of the overflow rather than the rim. How Deep Is the Water Really in a Walk-In Tub? covers the other reasons a measured depth can look wrong.

If Your Measurement Does Not Match the Spec

If the depth you measure at home does not match the published figure, or you want a fit check before ordering, send your model, your seated measurements, and a photo of the overflow with a tape measure held from the seat or the floor through ellasbubbles.com/support. Your Ella dealer or the team at (800) 480-6850 will confirm the depth for your unit and help match your numbers to a model.

Watch: How to Measure the Soaking Depth in Your Walk-In-Tub | Ellas Bubbles with chapters and a full transcript.

Related Guides

• Interior Length, Seat-to-Overflow and Seat-to-Footwell by Model: The Soaking Depth Table
• Seat sizes and soaking depth: how to measure yourself for a comfortable fit

Common Questions