How many Litres is a bathtub of water?

Quick Answer

The average bathtub holds between 150 and 200 litres of water. However, the exact capacity can vary greatly depending on the size and shape of the tub. Standard tubs generally range from 100 to 250 litres.

Measuring Bathtub Capacity

Determining the exact capacity of a bathtub requires measuring its dimensions and doing some calculations. Here are the steps:

  1. Measure the length, width and depth of the tub in centimetres.
  2. Multiply the length x width x depth to get the volume in cubic centimetres.
  3. Convert cubic centimetres to litres by dividing by 1000.

For example, if a bathtub is 150 cm long, 75 cm wide and 50 cm deep:

  • Length x Width x Depth = 150 x 75 x 50 = 562,500 cm3
  • 562,500 cm3 / 1000 = 562.5 litres

So this hypothetical tub would hold approximately 562.5 litres when filled to the brim.

Standard Bathtub Sizes

While exact capacities vary, most household bathtubs conform to standard dimensions:

Type Length Width Depth Average Capacity
Standard 150-170 cm 70-80 cm 40-45 cm 150-200 litres
Corner 140-150 cm 70-80 cm 40-45 cm 120-160 litres
Walk-in 150-170 cm 75-90 cm 40-50 cm 180-250 litres
Freestanding 160-200 cm 80-100 cm 45-55 cm 200-300 litres

As shown, a standard 5-6 ft rectangular tub holds 150-200 litres when full. Smaller corner tubs may hold 120-160 litres. Larger walk-in or freestanding tubs range from 180 up to 300 litres.

Factors That Affect Capacity

Several factors can alter the capacity of a bathtub, including:

  • Shape – Unusual shapes other than rectangular decrease overall volume.
  • Dimensions – Larger and deeper tubs hold more water.
  • Displacement – A person’s body displaces water when bathing, reducing real water volume.
  • Fixtures – Items like taps and drains also take up space.
  • Slope – Sloped sides result in less capacity than straight sides.

For example, a tapered tub that is wide on one end but narrow on the other will have a lower volume than a standard rectangular tub with the same maximal dimensions.

Estimating Capacity Without Measuring

It’s often convenient to estimate a bathtub’s capacity without taking detailed measurements. Here are some shortcuts:

  • Standard tubs: Estimate 150 litres
  • Large/deep tubs: Estimate 200+ litres
  • Smaller corner tubs: Estimate 100-130 litres
  • Multiply length x width x avg. depth x 0.004 to get an approximate volume in litres.

So for a 60 inch (150 cm) x 32 inch (80 cm) tub with an estimated 15 inch (40 cm) average depth:

  • 150 cm x 80 cm x 40 cm = 480,000 cm3
  • 480,000 cm3 x 0.004 = 192 litres (approximate volume)

These shortcuts provide reasonable estimates for most common tub sizes and configurations.

Comparing Bathtub Capacity to Other Liquid Volumes

To put bathtub water volumes into perspective, here’s how they compare to some other common liquid amounts:

  • Standard 350ml soda can – Less than 1/5 of a bathtub’s capacity
  • 750ml wine bottle – Around 1/4 bathtub volume
  • 18.9 litre / 5 gallon water jug – Roughly 1/10 of a tub
  • 190 litre / 50 gallon drums – Holds about the same as an average tub
  • 380 litre / 100 gallon hot tub – Twice the volume of most bathtubs
  • 3000+ litre in-ground pool – 10 times or more capacity

While a bathtub may seem small compared to a pool, it actually takes a surprisingly large amount of water to fill one up!

Water Usage Factors

Beyond just capacity, the amount of water used per bath can vary based on other considerations:

  • Initial fill level – Filling only 1/4 full uses less water.
  • Bather immersion – A fully immersed bather displaces more water out.
  • Bathing time – Quick showers use less than soaking for an hour.
  • Draining behavior – Pulling the plug immediately vs. letting water linger.
  • Leakage – Small leaks can waste water over time.
  • Frequency of bathing – Daily baths use more water than occasional baths.

The average bath takes 150-200 litres of water initially. But the real amount consumed depends on how much care is taken to minimize water usage before, during and after the bath.

Water Efficiency Tips

Here are some tips to maximize water efficiency when using a bathtub:

  • Take shorter 5-10 minute showers rather than baths.
  • Install a low-flow showerhead to reduce water usage.
  • Fill the tub only partially if a full bath isn’t needed.
  • Plug the drain before running water to avoid waste.
  • Turn the tap off while lathering up in the bath.
  • Reuse bath water for irrigating plants if sanitary.
  • Check for leaks and repair them promptly.
  • Share bath water with a partner or child.
  • Upgrade to a water-efficient tub if replacing an old model.

With some minor habit and hardware changes, the water used for bathing can be substantially reduced.

Measuring Software

Special apps and calculators are available to help measure bathtub capacity and water usage. Some popular options include:

  • Tubulator – Mobile app for measuring tub volume based on dimensions.
  • eWater – Web app to calculate home water usage for sinks, showers, tubs and more.
  • Water Use It Wisely – Bathtub and shower calculators using household size and flow rates.
  • Home Water Works – Interactive calculators for common water fixtures and appliances.
  • Waterwise – UK-based water efficiency site with a bathtub litre calculator.

These tools remove the math hassle and provide instant capacity estimates. They also help identify the biggest water using culprits at home.

Bathtub Size Regulations

In some regions, bathtub size regulations exist to ensure safety and access for users:

  • UK regulations state bathtubs must hold at least 150 litres (330 lbs) of water.
  • US ADA standards require public bathtubs to be at least 60 inches (150 cm) long.
  • Australian standards recommend a minimum 110 litre capacity for disability access.
  • Bathtubs between 150-250 litres are recommended to enable immersion bathing.

Building codes and accommodation laws generally set a lower limit for tub size and water volume. This ensures disabled and special needs persons can access suitably large baths.

World Record Bathtubs

At the extreme end, record-setting bathtubs have pushed the upper limits of bathing capacity:

  • World’s largest tub – 19 ft x 98 ft holds 66,000 gallons (250,000 litres).
  • Largest hot tub – 24 ft diameter and over 13 ft deep.
  • Highest tub – Installed in aHong Kong highrise 645 ft above ground.
  • Gold bathtub – Valued $1.1 million and made with over a tonne of 18k gold.

While these record tubs are outliers, they demonstrate the immense scale baths can reach far beyond the confines of a normal bathroom. The possibilities are as endless as one’s imagination!

Conclusion

A standard bathtub with average dimensions holds 150-200 litres of water when full. Smaller corner tubs may contain only 100-130 litres, while larger and deeper models can exceed 250+ litres. The many factors that influence capacity include the tub’s shape, precise dimensions, presence of fixtures and slope of sides. With some simple measurements and calculations, determining the exact volume a specific tub can hold is relatively straightforward. While bathroom tubs may seem tiny compared to larger bodies of water, they still require a surprisingly large volume to fill up for a nice hot soak.

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