Acrylic vs Cast Iron Tub (2026): Plus Enameled Steel and Fiberglass Compared

Short answer: Cast iron is the more durable, heavier, higher-cost tub: its thick enameled body resists scratches and keeps bathwater hot longer, but a typical cast iron tub weighs roughly 300 to 500 lbs empty. Acrylic is light, warm to the touch, available in more shapes, and easier to install, but it scratches more easily (light scratches can be polished out). Enameled steel has a similar enamel finish for less money and weight but chips more easily, and fiberglass is a low-cost, very light option with a typical lifespan of about 10 years (This Old House).

Acrylic vs cast iron vs steel vs fiberglass at a glance

A dash means the sources we checked don't make a clear claim for that material. Weights are manufacturer spec-sheet figures for specific models, not category averages.

What is the difference between acrylic and cast iron?

An acrylic tub starts as a sheet of acrylic that is heated, vacuum-formed into the tub shape, and backed with fiberglass reinforcement. Because the sheet can be molded, acrylic can be formed into shapes that cast iron cannot, from basic drop-ins to deep freestanding soakers.

A cast iron tub is made by pouring molten iron into a mold and then coating it with porcelain enamel. The result is a thick, rigid, very heavy tub with a hard, glossy finish. Cast iron is sold in alcove, freestanding and clawfoot styles; Kohler's lineup includes all three.

Durability

Cast iron is the most durable tub material. Its thick enamel resists scratches and dents, and Kohler backs its enameled cast iron baths with a lifetime limited warranty. The weak point is the enamel: a hard impact from a dropped object can chip it. Acrylic is non-porous and more durable than fiberglass, but its surface can scratch. Cheap acrylic tubs can also flex underfoot.

Heat retention

Cast iron's thick body keeps bathwater hot longer, which is why it is the classic choice for long soaks. The tradeoff is that iron conducts heat: a cold cast iron tub draws some warmth out of the first water you run. Acrylic feels warm to the touch right away, so you can lean back as soon as it's filled, and it holds heat better than fiberglass.

Weight and floor support

This is the biggest practical difference. Kohler's spec sheets list four of its 60-inch cast iron alcove tubs at 310 to 351 lbs, compared with 70 to 75 lbs for two of its 60-inch acrylic drop-in tubs. Cast iron installation is harder and costlier, and This Old House mainly recommends cast iron for ground floors. For an upstairs bathroom, have the floor checked and reinforced if needed.

Don't forget the water. Water weighs about 8.3 lbs per gallon, so Kohler's cast iron Villager (316 lbs, 33-gallon capacity) weighs close to 600 lbs filled, before anyone gets in. A deep acrylic tub is lighter empty but holds more water: Kohler's acrylic Archer (70 lbs, 58 gallons) weighs over 550 lbs filled. Manufacturers list a "minimum floor load" on each spec sheet; ask your contractor to compare it with your floor.

Cleaning and repair

Both are easy to wipe clean. For acrylic, Kohler says to use a soft cloth or sponge and never abrasive cleaners, brushes or scouring pads. Light scratches and dull spots can be buffed out with a polishing compound. On cast iron, small chips can be filled and touched up. A worn tub can be refinished, but a sprayed-on finish is not the original fired enamel. This Old House says a refinished cast iron surface should last 15 to 20 years with nonabrasive, bleach-free cleaning.

Cost

Cast iron is usually the most expensive tub material, and heavy tubs cost more to deliver and install. Acrylic sits in the middle: it costs more than fiberglass or enameled steel and less than cast iron.

Cast iron vs enameled steel tub

Enameled (porcelain-on-steel) tubs and cast iron tubs both have a porcelain enamel surface. What's underneath is very different. A steel tub is formed from steel sheet with a thinner enamel coat, while a cast iron tub is thick, cast iron.

• Weight: Steel is far lighter. The Bootz Aloha, a 60" x 30" steel alcove tub, lists 67 lbs, compared with 310–351 lbs for Kohler's 60-inch cast iron alcove tubs.
• Chips and rust: Steel's thinner enamel is more likely to chip or crack than cast iron's, and exposed steel can rust.
• Heat and noise: Thin steel lacks cast iron's insulating and sound-deadening mass, so filling the tub is louder. Some steel tubs add a sound-deadening pad or insulated backing. American Standard's Americast, for example, bonds porcelain-enameled steel to a structural composite backing.
• Cost: Enameled steel is one of the least expensive tub types, while cast iron is one of the most expensive.

Bottom line: Choose steel if you want an enamel finish on a budget or can't handle cast iron's weight. Choose cast iron if you want the most durable enamel and the best heat retention.

Fiberglass vs cast iron bathtub

These are opposite ends of the market. Fiberglass (FRP) tubs are glass fiber and resin with a gelcoat surface. They're the lightest and cheapest tubs you can buy.

• Lifespan: This Old House puts a typical fiberglass tub at about 10 years, versus a potential 70 years for cast iron.
• Surface: Fiberglass is porous enough to absorb water, so stains can be hard to remove, and the color can fade with repeated cleaning. Cast iron's enamel resists stains and scratches.
• Feel: Inexpensive fiberglass tubs can flex and feel less solid underfoot.
• Repair: Fiberglass is easy and inexpensive to repair. Cast iron is harder to damage, but enamel chips need touch-up or refinishing.
• Weight and install: Fiberglass is lightweight and simple to install. Cast iron is heavy, installation is harder and costlier, and some floors need reinforcement.

If fiberglass is your budget and you want something sturdier, acrylic is the usual step up. It's more durable than fiberglass and holds heat better.

Acrylic vs cast iron clawfoot tub

Clawfoot tubs are freestanding tubs on claw-shaped feet. They are made in both cast iron and acrylic.

• Weight: Cast iron clawfoot and freestanding tubs are among the heaviest tubs made. Kohler's cast iron Birthday Bath (72" x 37-1/2") lists 430 lbs empty, and its ball-and-claw feet are a required separate accessory. An acrylic clawfoot is much easier to carry upstairs.
• Load on the floor: A clawfoot rests on four feet instead of a full base. Have your contractor check the floor where the feet will sit, especially for cast iron.
• Heat: A freestanding tub is exposed on all sides. Cast iron's mass helps hold heat, while acrylic feels warmer to the touch from the start.
• Finish: On Kohler's freestanding cast iron models (Birthday Bath, Vintage), the exterior is painted rather than enameled. Kohler notes that painted exterior smoothness can vary from tub to tub.

The Altair Geneva is an acrylic clawfoot tub, 68.9"W x 29.9"D x 29.5"H, with chrome-finish alloy claw feet and a brass pop-up drain. Its product page notes that the overflow and faucet are not included.

Are there bathtubs better than acrylic?

It depends on what "better" means to you. For heat retention and durability, cast iron outperforms acrylic. Insulated enameled steel, like Americast, is a lighter-weight alternative to cast iron. Fiberglass and plain enameled steel usually cost less than acrylic, but fiberglass is less durable and steel's enamel chips more easily. Some freestanding tubs use a reinforced acrylic composite, which is heavier than a basic acrylic shell. For example, the KubeBath Kube Squadra lists "Reinforced Acrylic Composite Construction" and weighs 147 to 173 lbs depending on size, versus about 70 lbs for a basic acrylic drop-in.

Many tubs combine materials. The MediTub 3260LWS walk-in tub, for instance, lists "high grade marine fiberglass with acrylic coating" on a stainless steel frame. You can browse freestanding acrylic soakers such as the Altair Allegra, plus walk-in tubs, in our bathtubs collection.

Which tub should you buy?

• Long, hot soaks, and a floor that can take the weight → cast iron
• Upstairs bathroom, DIY install, or a deep freestanding shape → acrylic
• Vintage clawfoot look without the 400+ lb weight → acrylic clawfoot
• Enamel finish on a tight budget → enameled steel (look for insulated or padded versions)
• Low cost and light weight, with a shorter expected lifespan → fiberglass

Frequently asked questions

Is a cast iron or acrylic tub better?
Cast iron is better for durability and keeping water hot. Acrylic is better for weight, easier installs, and variety of shapes, and it costs less. If your floor can support the weight and you soak often, cast iron is worth it. Otherwise, a good acrylic tub is the practical choice.

What are the pros and cons of acrylic vs cast iron?
Acrylic pros: light, warm to the touch, many shapes, and minor scratches can be buffed out. Acrylic cons: softer surface that can scratch, and cheap models can flex. Cast iron pros: very durable, scratch-resistant, and holds heat. Cast iron cons: roughly 300 to 500 lbs empty, higher cost, harder installation, and chipped enamel needs touch-up.

How much does a cast iron tub weigh?
Most weigh roughly 300 to 500 lbs empty. Kohler's spec sheets list 310 to 351 lbs for four of its 60-inch alcove models and 430 to 485 lbs for two freestanding models. Add about 8.3 lbs per gallon of water.

Is a steel tub as good as cast iron?
Not quite. Enameled steel has a similar glossy look and costs less, and it is much lighter. Its enamel is thinner and chips more easily, and exposed steel can rust. It also doesn't hold heat or muffle noise like cast iron unless it has insulated backing.

Do cast iron tubs chip?
The enamel is very hard, but a heavy impact can chip it. Small chips can be filled and touched up, and a worn tub can be professionally refinished. Clean with nonabrasive products to protect the finish.

Questions? Call or text (916) 262-7257 or email support@archicfurniture.com.