Bathtub Capacity | How Much Water Does The Average Bath Hold?

Did you start having a bubble bath once a week and just got your water bill? Wow, that was high. How much water is going into your supersized tub and what exactly is your bathtub capacity?

Perhaps you are planning on adding a bathroom upstairs and want to know just how much weight will be added to the structure of the building.

In this post, I’ll look at how much water fits into your bathtub and how much it weighs.

Let’s dive in!

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What Is The Average Bathtub Size And Its Capacity?

The average bathtub size in the UK is 1700mm (L) x 700mm (W) x 545mm (H). If you filled it to the top, it could hold approximately 300 litres of water.

However, most baths have an overflow at about the two-thirds full mark, so that limits just how full it will get.

Many people will only fill the tub about halfway for their morning soak. If you are planning on an extended wallow under the bubbles, you might fill it right to the overflow.

For practical purposes, you might expect to use about 200 litres of water for an average-sized bath.

Small Bathtub Size And Capacity

An average small bath will measure about 1400mm x 700mm x 400mm. But remember that is your outer dimension! The smaller tub will hold a maximum of 150 litres within its walls. You might use about 100 litres to fill it for a bath for your kids.

A small bath is a good option for a shower/bath combination when you expect to use it as a shower the majority of the time. The tub is still big enough for younger children or the dog but might be disappointing as an adult-sized soaking experience.

Large Bathtub Size And Capacity

Do you have a tub that lets you really get comfortable? An average large bath comes in around 1800mm x 800mm x 545mm with a maximum capacity of 410 litres. You will enjoy a good bubble bath using around 300 litres. 

Large tubs are often found in luxury ensuites in contemporary homes. In some instances, they are designed to seat two adults. You might have jets hidden in the sides. They will not affect its water capacity, but it does add extra weight to the actual bath.

Freestanding Bathtub Size And Capacity

A freestanding bath is usually about the same size as a large tub, holding around 400 litres at the max. A true antique bath may not have an overflow, so you potentially could fill it to the top.

Freestanding baths tend to be made out of steel or cast iron, so the weight of the bath should also be considered when thinking about building a structure to hold the weight of all the water.

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What Is The Average Bathtub Size And Its Capacity?

How Heavy Is A Bathtub Full Of Water?

A litre of water weighs one kilogram, which makes this an easy calculation. If you have 150 litres of water in the bath, it will weigh 150 kg.

The large-sized tub will hold up to 400 kg of water. A small tub will hold around 150 kg of water.

If you are calculating just how heavy a full tub will be when building a bathroom in a top floor flat, remember to include the weight of the person and the bath itself.

Your bath can be as light as 25 kg if it is fibreglass. A vintage cast iron tub could weigh up to 250 kg or more. An average adult will tip the scales at about 85 kg.

Are you adding a hot tub that seats several people? Ask your salesperson for the maximum water capacity and add the weight of potential guests plus one to get a solid number for your builder to use. 

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How Many Litres Of Water Is A 10-Minute Shower?

Most households in the UK enjoy a water flow rate of about 15 litres per minute. So, an average 10-minute shower will use about 150 litres.

If you have low water pressure or install a water-saving showerhead, your water flow for the shower can be as low as 9 litres/minute. That can reduce your quick shower usage to just 90 litres.

Do you remember the old shower in your parents’ home? Those classic showerheads were capable of pouring 20 litres/minute on your head.  Now you are guzzling nearly 200 litres for a quick refresh.

What happens when you spend five minutes more and take 15mins under the steamy shower? It kicks up to 225L on average with a low of 135L and up to 350L in that luxurious rain shower.

Did you spend 20 minutes for a really good think under the water? You used 180L up to 400L!

How does that compare to a long soak in a tub? Since you don’t keep refilling the bath, your water-saver showerhead running for 20 minutes uses a little less than filling your standard bath to the overflow. When you opt for the 10-minute quickie, you saved half the water!

How Many Litres Is A 10-Minute Shower?

How Much Water Can I Save By Taking A Shower vs. A Bath?

If you trade your daily soak in 200L of bath water for a 150L 10-minute shower, you are reducing your water usage by 25%. That adds up to a potential water saving of 18,000L per year for just one person.

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My Water Bill Is Unmetered: How Do I Save By Using Less Bath Water?

Even though you are paying a flat tariff for your water every year, you do pay to heat the water by volume. Most hot water in a house is used for bathing and showers.

If you switch to taking a fast shower from filling the tub, you can reduce your water heating bill by one third to a half.

However, more and more homes are converting to a measured water bill. So reducing water usage in your shower will directly reduce your quarterly or annual tariff.

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Final Thoughts…

There you have it! Everything you need to know about bathtub capacity. As well as a little bit of extra information.

For most, knowing your bathtub capacity and weight won’t matter too much, especially if the bath is being installed on the ground floor. However, for those putting a bath upstairs or in an attic/loft conversion, the capacity and weight of the bathtub can be an important factor.

Also, knowing your bathtub capacity informs you of how much water you’re really using. So you can make a fair comparison to showing and decide which option is best for you and the environment.

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Michael R

Michael is a KBB designer from the UK. He's been designing and project managing new Kitchen, Bedroom and Bathroom installations for over eight years now, and before that, he was an electrician and part of a KBB fitting team. He created The Bathroom Blueprint in early 2020.