How many litres in a standard bath?
A standard tub holds 150–200 litres to the overflow — about 180 is typical. But that brim figure answers the wrong question. The number that matters is the ~80 litres you actually use, because that's what decides the real question behind the search: is a bath more wasteful than a shower?
Bath vs shower — which uses less?
set your numbersA bath is a fixed amount of water; a shower depends entirely on the head and the clock. Find the break-even for your setup.
The bath uses less here. At 10 L/min, your shower matches this bath at 8 minutes — shorter and the shower wins, longer and the bath does. Heating the bath takes roughly 2.4 kWh.
Energy figure heats the bath water from a 14°C inlet to 40°C; it ignores standing losses. Water-only comparison otherwise.
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"200 litres" is the brim, not the bath
The figure people repeat is the tub's capacity to the overflow, which for a standard rectangular bath is around 150–200 litres; Waterwise and the Energy Saving Trust's At Home with Water report put the typical tub near 180 litres (about 60 US gallons). You almost never fill to that line, though, and once you climb in your body displaces another 60–70 litres. Waterwise's working figure for the water actually used in a bath is about 80 litres — less than half the brim number. Quote 200 and you're describing an empty tub; quote 80 and you're describing a bath.
The bath-vs-shower break-even most people get wrong
"Showers always use less" is a half-truth. A standard showerhead runs about 10–15 litres a minute (Smart Energy GB), so an 80-litre bath is matched at roughly 7–8 minutes on a 10 L/min head. Stay under that and the shower wins; linger past it and the bath does. The trap is the power shower: NI Water measures one at about 90 litres for a typical wash — basically a bath with extra steps — while a brisk five minutes under a standard head is only ~35 litres. For scale, the US 2016 Residential End Uses of Water study found the average American shower runs ~7.9 litres a minute for ~7.8 minutes, around 60 litres. The widget above lets you drop in your own head and habit and read off your personal break-even.
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The cost is mostly heat, not water
The water in a bath is cheap; warming it is not. Lifting one litre by one degree takes 4.186 kilojoules, so heating 80 litres from a typical 14°C mains inlet (Energy Saving Trust monitoring) to a 40°C bath is about 2.4 kWh — the same energy as running a typical microwave for well over an hour. The Energy Saving Trust attributes roughly 12% of a UK household's energy bill to heating water; the US Department of Energy puts water heating at a larger share of household energy. The practical lever, then, isn't really bath-versus-shower — it's how hot and how full, for both.
The tubs that break the "standard" figure
"Standard" hides a lot of range. A Victorian-style cast-iron clawfoot tub is deeper than a modern fitted bath and can hold closer to 250 litres at the brim. At the other extreme, a Japanese ofuro soaking tub is short in footprint but deep enough to submerge you sitting upright with knees bent — washing happens outside the tub, and the same water is often reheated and reused across a household, which makes its real per-person water use far lower than the volume suggests. The "standard bath" is a Western fitted-rectangle convention, not a law of plumbing.
Frequently asked
How many litres are in a standard bath?
About 150–200 litres to the overflow (≈180 typical), but only ~80 litres actually used once you fill below the line and account for your body displacing water.
Is a bath or a shower cheaper?
It depends on flow rate and time. An 80-litre bath equals roughly 7–8 minutes of a standard 10 L/min shower. Shorter showers win; power showers (15+ L/min) lose to the bath in about 5 minutes.
How do I work out my own bath's capacity?
Length × width × depth-to-overflow in centimetres, divided by 1,000, gives litres to the brim. Subtract 60–70 litres for body displacement and remember you rarely fill that high.
How many gallons is a bath?
The ~80 litres used is about 21 US / 17.6 UK gallons. A full 180-litre tub is about 48 US / 40 UK gallons.
Why does heating cost more than the water?
Heating 80 litres from 14°C to 40°C is ~2.4 kWh. Water itself is a few cents; the energy to warm it is the bulk of a bath's cost.
Sources
- Waterwise (UK water-efficiency NGO) — average bath ≈ 80 litres used; typical tub ≈ 180 litres / 60 US gallons to the brim.
- Energy Saving Trust — At Home with Water report; ~14°C mains inlet (2008 monitoring); ~12% of a UK household energy bill goes to heating water.
- Smart Energy GB — standard showerhead ≈ 10–15 litres per minute; a 10-minute shower ≈ 100–150 litres.
- NI Water / Get Water Fit — power shower ≈ 90 litres; a 5-minute standard shower ≈ 35 litres.
- US EPA WaterSense & the 2016 Residential End Uses of Water study — average US shower ≈ 7.9 L/min for ≈ 7.8 minutes (~60 litres).
- Specific heat of water = 4.186 kJ per litre per °C (used for the kWh estimate).
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Related
The honest answer to "how many litres in a bath" isn't 200 — it's whatever you put in, and the only number your water bill ever sees is 80.