The standard size of a bath in the UK has varied over the years, but the most common size for a standard modern rectangular bath is 1700mm x 700mm (approximately 5 ft 7 in x 2 ft 3 in). This gives a typical standard UK bath volume of around 300 litres. However, there are some variations and options to consider.
Typical UK Bath Dimensions
While a standard 1700 x 700mm bath size is common, some key dimensions to note include:
- Length – Standard bath lengths tend to range from 1500mm to 1800mm. 1700mm is the most common.
- Width – Standard widths range from 650mm to 750mm. 700mm is typical.
- Depth – Standard bath depths are often between 400mm to 600mm. Most common depth is around 450mm.
Based on these typical dimensions, a standard modern UK bath size can be summarized as:
- Length: 1700mm (5 ft 7 in)
- Width: 700mm (2 ft 3 in)
- Depth: 450mm (1 ft 5 in)
This gives a typical bath interior capacity of around 300 litres. However, with variations in sizing, the actual volume can range from 200 litres up to over 400 litres.
Standard Rectangular Bath Volume
Using the standard dimensions of 1700mm x 700mm x 450mm (length x width x depth):
- Length: 1700mm = 1.7m
- Width: 700mm = 0.7m
- Depth: 450mm = 0.45m
The volume of a rectangular bath is calculated as:
Volume = Length x Width x Depth
Therefore, the volume of a standard 1700 x 700mm bath is:
= 1.7 x 0.7 x 0.45
= 0.51 m3
As 1 cubic metre (m3) = 1000 litres
0.51 m3 = 510 litres
So the total volume of a standard 1700 x 700mm UK bath is approximately 510 litres.
However, baths are rarely filled to the brim. A typical fill depth is around 300-350mm.
At a fill depth of 300mm:
Volume = 1.7 x 0.7 x 0.3
= 0.357 m3
= 357 litres
Therefore, a standard 1700 x 700mm UK bath, filled to a typical depth of 300mm contains approximately 357 litres of water.
Typical modern standard UK bath volume
To summarize, while a standard 1700 x 700mm full bath volume is around 510 litres, typical real-world fill volumes are lower.
With a common fill depth of 300-350mm, the actual volume of water in a standard modern UK bath is:
- At 300mm fill depth: 357 litres
- At 350mm fill depth: 419 litres
So the typical volume of water in a standard modern UK bath is between 357 and 419 litres, with 350 to 400 litres being common.
Factors affecting bath volume
While a standard 1700 x 700mm sized bath with a 300-350mm water depth is typical, there are some variations to consider:
Bath Length
Longer baths can hold more water. A 1800mm long bath can hold over 100 litres more than a 1500mm shorter bath.
Bath Width
Wider baths also increase capacity. A 750mm wide bath holds around 50 litres more than a narrower 650mm wide bath.
Depth
Shallower baths 400mm deep hold less water than deeper 500-600mm models. Depth affects capacity as well as fill volume.
Bath Shape
Whilst rectangular baths are most common, other shapes like oval, triangular or square can vary capacity.
Water Fill Depth
The actual volume when in use depends on the amount of water put in the bath, which can vary per person or usage.
Water Displaced
The volume of water displaced by a person getting into a bath also lowers the actual water capacity available.
Non-standard bath sizes
Whilst 1700 x 700mm is the most common size, other dimensions are also available:
Larger Baths
Larger baths may be 1800-1900mm long and 750-800mm wide. These can hold 400-500 litres fully filled.
Smaller Baths
Smaller baths 1500-1600mm long and 650-700mm wide for squeezed spaces hold 200-300 litres.
Corner Baths
Shaped to fit a corner, these angled baths often hold less volume than standard rects.
Double Ended Baths
With a rounded end at each end, capacity varies but is often 300-400 litres.
Slipper Baths
Older style single ended baths with one rounded and one flat end tend to hold less than modern baths.
Measuring bath capacity accurately
To measure bath volume more precisely:
- Measure the internal length, width and depth dimensions in mm or m.
- Calculate the rectangular volume using the formula: Length x Width x Depth.
- Convert cubic metres result into litres (x 1000).
- Measure and account for any shallow or sloped areas.
- Determine typical fill depth and calculate volume.
- Measure actual filled volume by draining the bath into buckets.
This will give a more accurate measure of actual bath capacity and fill volumes.
Typical bath fill volumes
While the full volume may be 300-500 litres, typical bath fill volumes are less. Some approximate fill volumes include:
| Fill Depth | Fill Volume (1700x700mm Bath) |
|---|---|
| 100mm | 119 litres |
| 150mm | 179 litres |
| 200mm | 238 litres |
| 250mm | 298 litres |
| 300mm | 357 litres |
| 350mm | 417 litres |
This shows that common fill depths of between 300mm and 350mm typically use between 357 to 417 litres of water.
Bath capacities by bath type
Approximate full and typical fill capacities for different bath types:
| Bath Type | Typical Full Capacity | Typical Fill Volume |
|---|---|---|
| Standard Rectangular 1700x700mm | 510 litres | 357-417 litres |
| 1800x800mm Rectangular | 720 litres | 450-540 litres |
| 1500x700mm Small Rectangular | 315 litres | 220-260 litres |
| 1700x750mm Rectangular | 383 litres | 270-320 litres |
| Double Ended 1700x750mm | 380 litres | 266-318 litres |
| Corner Bath 1200x1200mm | 288 litres | 202-242 litres |
This shows standard baths have capacities of 300-500 litres, with typical used volumes around 250-400 litres.
Water usage when filling a bath
The amount of water used to fill a bath depends on its volume and the flow rate of water entering it.
With a standard 350 litre bath, filled at a flow rate of:
- 8 litres per minute – Takes 44 minutes to fill bath, using 352 litres
- 10 litres per minute – Takes 35 minutes, using 350 litres
- 15 litres per minute – Takes 23 minutes, using 345 litres
- 22 litres per minute – Takes 16 minutes, using 352 litres
So at typical modern flow rates of 12 to 15 litres per minute, it takes 300 to 350 litres and 20 – 30 minutes to fill a standard 350 litre bath.
Power showers over 20 litres per minute can fill it more quickly but use similar volumes of water.
Baths with capacities from 200 to 500 litres when filled will therefore use approximately this much water.
Water usage bathing vs showering
| Bathing (300 litre bath) | Showering (6 litres/min) |
|---|---|
| 300 litres per bath | 36 litres for a 6 minute shower |
| 20-40 minutes to fill bath | 6-10 minutes to shower |
| Can share bath water with partner | Water goes straight down the drain |
This shows that baths use far more water overall. However, showers typically flow at 6-10 litres per minute, so a 10 minute power shower can use 60-100 litres.
Tips for saving water when bathing
Ways to reduce water usage when bathing include:
- Take shorter showers instead of baths
- Install a low-flow showerhead to use less water
- Share bathwater with a partner or child
- Fill bath halfway or to a lower level
- Turn tap off while soaping and scrubbing
- Install a displacement device to reduce filled volume
- Re-use bath water for cleaning or watering plants
Following these tips when bathing can help significantly reduce indoor water usage.
How bath volume relates to water bills
The cost impact of filling a bath depends on:
- Number of baths taken per week
- Number of household occupants bathing
- Volume of water used per bath
- Water rates and billing per cubic metre
For example, with a 300 litre bath, filled 3 times per week by one person:
- 300 litres x 3 baths per week = 900 litres
- 900 litres per week x 52 weeks = 46,800 litres per year for one bather
- At a water rate of £1 per cubic metre = £46.80 annual bathing cost
For a family of four taking a total of 14 baths per week:
- 900 litres x 14 baths = 12,600 litres weekly
- 12,600 litres x 52 weeks = 655,200 litres per year
- 655 cubic metres x £1 per m3 = £655 annual cost
Reducing water volumes used or frequency of bathing can therefore generate significant savings over a year.
Conclusions
To conclude:
- A standard modern UK bath size is around 1700 x 700mm.
- This has a full volume of around 300-500 litres.
- Typical used bath fill volumes are 150-400 litres.
- Baths use far more water than an equivalent shower.
- Saving water when bathing reduces environmental impact.
- Lower water usage also reduces household bills.
Carefully considering bathing frequency and fill levels allows enjoying a good soak while saving water.