How to Measure a Bathtub—Standard Tub Sizes & Measuring Guide
January 12, 2022
By Mikael Short
The size of your tub can make or break the bathing experience. A short, shallow tub is unlikely to provide a soothing soak. On the other hand, a tub that’s too large for the space can make it challenging to use the rest of the bathroom.
Most importantly, you don’t want to find out when your tub arrives that you ordered the wrong size! Returning a tub or retrofitting your bathroom for the new tub size can be a timely and costly endeavor. Correctly measuring your bathroom and designated tub area the first time ensures a much smoother installation experience.
Bathtub Measurements 101
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:
However, some tubs simply go by the overall length:
Regardless, always check both the product details and the attached specification sheets for tub measurements before purchasing a new tub.
How to Measure a Bathtub
Not only do you need the correct size of the tub, but you also need to know the amount of space available in your bathroom. Keep in mind that wherever the plumbing is will determine where your tub should go.
Don’t just measure the existing tub if you have one. Measure the space around where you expect your tub to be to ensure a workable fit.
1. Identify the Plumbing
First and foremost, identify where the new tub will be placed. If you’re replacing an old tub, this should be fairly easy. However, if you’re building your bathroom from scratch (or completely remodeling your bathroom), determine where the plumbing is set up or will be set up to allow for a new tub. This is the space you will measure.
2. Measure the Designated Tub Area for the Overall Width, Length, & Height
Measuring the length and width of the designated tub area is the best place to start to get an idea of how much space is actually available for a bathtub. These measurements will give you the maximum overall width, length, and height your tub can be.
Most tubs sit parallel against the wall, so you’ll want to start by measuring the length of the wall to help gauge how long your tub can be. Then, measure the width of the area by measuring out from the wall to the furthest point you expect your tub to be wide.
If the tub is enclosed in an alcove, measure from wall to wall (or side to side) and then from the back wall forward for the width.
For drop-in and undermount tubs, be sure to also remove an inch from the overall width and length for the lip of the tub to fit comfortably within the frame.
Measuring the height of the space ensures the tub won’t conflict with any outlets or ledges. The most common bathtub height is around 15-16 inches.
Keep in mind that deeper tubs may have taller walls to step over. Plan accordingly so you can enter the tub safely, either at a safe height or with steps.
3. Plan for Basin Clearance
Also, plan for enough clearance, or free space, surrounding the tub to enter and exit safely. Ideally, 60” x 30” is considered sufficient clearance around the entrance of the tub.
The rule of thumb for the distance between other bathroom features includes 12 inches away from vanity cabinets and 21 inches away from the front of a toilet.
Also, remember to measure your doorways and hallways to ensure the tub will fit when it’s delivered and installed.
4. Measure for Comfort—Basin Length, Width, and Soaking Depth
Once you understand the space you’re working with and know the general height, width, and length of your tub, it’s time to measure for your desired basin size and soaking depth.
To start, consider how the tub will be used and by whom so you know how much space and depth you need.
If you prefer your old tub’s dimensions, use the following guide to measure for the desired basin length, width, and soaking depth.
Basin Size — Length & Width
The basin size is the interior length and width of the bathtub basin.
The basin length should be measured at its widest point in the middle of the tub, from left to right. The length always refers to the longest point of the tub.
To find the basin width, measure from the midpoint of the length of the tub, front to back.
The most common tub size is 60” long x 30” wide, though now a wide variety of sizes are available depending on the type of tub.
The soaking depth represents how much space you have to submerge in the tub basin. Standard tubs have around 12” soaking depth, but soaking tubs have 14+ inches.
To measure the soaking depth, measure from the lowest point in your tub (likely the drain) up the basin wall to the bottom of the overflow drain on the side.
5. Assess Tub Capacity & Overall Weight
Once you know the basin size you’re looking for, consider how much water that the size of the tub will hold, or the tub capacity. Ensure that the size of your water heater will hold enough water to correspond with the tub size. In general, the water heater should be about ⅔ of the tub size in order to fill it.
Consider how much weight your bathroom floor can hold (since the tub’s material will affect its weight). Take into account both the weight of the tub itself and the weight the water will add when the tub is at capacity. This step is especially important when browsing for cast iron tubs, which are often much heavier than standard tubs and require floor reinforcement.
What’s the ideal soaking size?
A soaking depth of at least 14 inches should be sufficient for many people to submerge most of their body under water.
Nowadays, bathtubs are made specifically with a comfortable soak in mind, with upwards of 14” of soaking depth. Soaking tubs often have high walls and shorter lengths to provide more coverage in soaking depth, much like the popular Japanese-style soaking tubs.
Having an idea of the basin length, basin width, and soaking depth will help you discover if a tub is big enough to let you soak comfortably inside.
Ultimately, it will boil down to your personal preference as well as your bathroom space capabilities to select a soaking tub that fits your needs.
Standard Tub Sizes for Different Types of Bathtubs
Alcove bathtubs are surrounded by three walls leaving one side open, sometimes two. Built into an alcove or recess in a bathroom, this style of tub is common with tub-shower combos. Up to three sides come unfinished since they install flush against the wall and aren’t exposed.
Alcove tubs are most common in small to medium-sized bathrooms as they fit tight spaces well. Their installation is among the easiest as well.
The standard size for an alcove tub is five feet long. However, alcove tubs are available in other sizes too. Depending on the size of the alcove, you could have a shorter tub to allow for a deck on one or both short edges of the tub.
Small Alcove Tub Size:
- Length: 54” (4.5 ft)
- Width: 30”
- Height: 15”
Moderate/Standard Alcove Tub Size:
- Length: 60” (5 ft)
- Width: 32”
- Height: 18”
Long/Large Alcove Tub Size:
- Length: 72” (6 ft)
- Width: 36”
- Height: 20”
As the name suggests, freestanding bathtubs stand on their own, either as pedestal tubs or with legs, such as the popular clawfoot tubs. Freestanding tubs most often pair with an exterior faucet that connects to the floor rather than the tub itself. The installation is straightforward and the placement is flexible for stand-alone tubs.
Oval tubs and soaking tubs are commonly found in freestanding designs.
Freestanding tubs come in a variety of sizes so you can find the right fit for your bathroom. Keep in mind that you’ll need clearance of at least three inches between the rim and the surrounding walls.
Standard Freestanding Tub Sizes:
- Length: 55” - 72” (about 4 1/2 to 6 feet)
- Width: 27” - 32”
- Height: 15” - 20”
Corner tubs are triangular-shaped tubs that fit into a corner of your bathroom, often as a drop-in, undermount, or alcove tub. Often they are as long as they are wide, which is nice for a spacious homeowner’s bathroom suite. It may be better to consider it as a square-shaped tub since it’s essentially a square-shaped space with a corner taken off in many designs.
Corner tubs are ideal for large bathrooms since they can take up a lot of space.
Standard Corner Tub Size:
- Length: 60”
- Width: 60”
- Height: 22”
Oval-shaped tubs appear larger than other models, and they are. They are usually made wider than other types of bathtubs. Beautiful oval tubs are available as a freestanding, drop-in, undermount, or soaking tub.
Standard Oval Tub Size:
- Length: 60”
- Width: 41”
- Height: 24”
Whirlpool / Air Bathtubs
Bathtubs with whirlpool jets or air jets are popular for a truly relaxing spa bathroom. A variety of whirlpool tubs come ready for standard alcove sizes and are often designed as drop-in tubs.
They often work better in medium to large bathrooms that can accommodate an alcove or drop-in tub. Some are also available in a walk-in tub.
Standard Whirlpool Tub Size:
- Length: 60”
- Width: 32” - 36”
- Height: 18” - 23”
Walk-in tubs are designed for those with mobility challenges, so you can step straight into the tub without climbing in through a side-panel door. Usually there’s a built-in seat as well as bars and anti-slip floors for safety purposes too. Many models also come with whirlpool functions as well to help with blood circulation and relaxation.
Walk-in tubs often come in a corner or alcove style and will most likely fit those standard dimensions.