Find out whether your bath or shower uses more water. Enter your shower flow rate, shower duration, bathtub size, and fill level to compare gallons used per wash — and see which option is kinder to the planet.
Water-Saving Winner
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Water Per Shower
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Water Per Bath
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Weekly Shower Usage
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Weekly Bath Usage
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Weekly Water Saved (vs Higher Option)
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Annual Water Saved
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It depends on your habits. A short shower (under 8 minutes) with a low-flow 2.5 GPM showerhead typically uses less water than a full bath. However, a long shower with a high-flow head can easily exceed a half-filled tub. Use this calculator with your real numbers to find out which wins for you.
Multiply your showerhead's flow rate (in gallons per minute) by the length of your shower in minutes. For example, a 10-minute shower at 2.5 GPM uses 25 gallons. The formula is: Gallons = Flow Rate × Duration.
A standard bathtub holds about 48 gallons (180 liters) when completely full. If you fill it three-quarters full, that's roughly 36 gallons. Smaller tubs hold around 37–42 gallons at capacity. The actual usage depends on your tub size and how full you fill it.
Modern low-flow showerheads are restricted to 2.5 gallons per minute (GPM) or less under US regulations. Older or non-restricted showerheads can flow at 3–5 GPM or more. Installing a low-flow showerhead is one of the easiest ways to cut water use.
With a standard 2.5 GPM showerhead and a half-filled tub (about 24 gallons), a shower would exceed bath usage after around 10 minutes. With a 5 GPM showerhead, you'd surpass that same bath in just 5 minutes. The break-even point shifts based on your flow rate and tub fill level.
Yes. A long hot shower with a high-flow showerhead can use significantly more water than a moderately filled bath. Power showers, for example, can use up to 17 litres (4.5 gallons) per minute, meaning a 15-minute shower could use 68 gallons — far more than most baths.
Install a low-flow showerhead (2.5 GPM or less), shorten your shower to under 8 minutes, turn off the water while lathering, and place a bucket to catch warm-up water for plants or flushing. These small changes can save thousands of gallons per year.
If a bath uses 10 gallons more than your shower, switching from 2 baths per week to showers saves around 1,040 gallons per year. Your exact savings depend on your flow rate, shower length, tub size, and how often you bathe — use the calculator above to get your personalised figure.