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Bath vs Shower Calculator

Created by Kenneth Alambra and Rahul Dhari
Reviewed by Bogna Szyk and Steven Wooding
Last updated: Jun 05, 2023

The fact that you are here is a testament that you are ready to do your bit for the planet. Almost two-thirds of our planet is water, and about the same fraction of the population suffers the hardship of securing access to clean water. According to UNICEF, four billion people at some point severe face water scarcity for at least a month every year. It is also projected that half of the world's population will be living in water scarce areas by early 2025. To further compound the issues, climate change is creating uncertain drought and flood patterns. Water scarcity will further cause agricultural, environmental, health, and economic crises and tensions on the geopolitical side.

You can do your bit to turn the tide against the water crisis by being "water-wise". Now, what is being water-wise? It is about being smart about your water usage to avoid excessive water use. For instance, did you know, water in the shower is among the top three primary household water-related activities after toilets and washing machines? You would be amazed how much water you can save by tweaking your bathing habits.

Even reducing your shower time by 2-5 minutes from the regular 10 minutes shower can shave off about 10-25 gallons (37-95 liters) of water while lowering your energy bills. Studies also indicate a cold shower can have health benefits like soothing itchy skins, relaxing sore muscles, and increasing your metabolism rate while reducing your energy consumption. These small changes can make a big difference to your health and environment. This calculator will help you estimate the water usage during your daily shower or bath and help optimize your water consumption to lower your water and energy bills, i.e., saving money and the environment at the same time.

As per the UK's Environment Agency, water usage during a 5-minute shower is only about a third of a bath. But a high flow or a power showerhead can take up to 136 liters of hot water, which is almost twice the amount of water than the bath. So what is more eco-friendly? – a bath or a shower?

Water consumption pattern in average household

Knowing is half the battle. So let us first understand water and energy consumption. This calculator will focus on your bath and shower habits to estimate your water utilization and the attached energy expenses. As per USGS data, here is the average water use for your daily activities:


Usage (in gallons)



Face/Leg shaving


Toilet flush

3 gallons per flush


Machine - 6-16 gallons per cycle*

Manual - 9-27 gallons

Clothes washing

25-40 gallons*


2-5 gallons per minute*


36-50 gallons (average)

*The usage of faucets and machines varies based on their age. Older faucets and dishwashers consume higher amounts of water.

As per the consumption data in the table above, we can see the significant contributor to water usage is a bath or shower. We believe changing bath habits can result in saving water and energy bills.

Estimating water usage for shower and bath

The calculation for showers is reasonably straightforward. Most new showerheads conform to the federally mandated limit for showerheads, i.e., not more than 2.5 gallons of water must come out of the shower per minute. Let's calculate water usage for a 15-minute continuous shower.

  1. Set showering style as continuous shower.
  2. Shower flow rate is set to a default value of 2.5 gallons per minute (gpm). This is not to be confused with flow speed, since we are interested in volume passing per unit of time.
  3. Enter the average shower duration, say 15 mins.
  4. Set the shower power as per your usage to 1/2, 3/4, or full.
  5. Fill in how many times a day you shower in Shower frequency, say 1.
  6. Total water consumption can be estimated as:
    Flow rate × time = 2.5 gpm × 15 minutes = 37.5 gallons

If you use a flow restrictor, you can cut water consumption by 50% or 25% when used at a half or ¾ power setting. Here's how:

  1. Select the showering style as staggered shower.
  2. Input the different durations for different stages of a shower, say 5 minutes each for initial, lathering, and rinsing.
  3. Pick the shower power settings, say you use the shower at 1/4 setting while lathering, and rest at full shower power.
  4. You consumed:
    Flow rate × time = 2.5 × 5 + 0.625 × 5 + 2.5 × 5 = 28.125 gallons

By using a flow restrictor, you just saved 9.375 gallons (35.49 liters) of water. The exact amount of water you use to brush your teeth more than 9 times or 150 cups (8 oz.) of water!

Now let's take a look at water consumption during a bath. To estimate water consumption during bath:

  1. Select your bathtub size from the list. Let's pick a 60-gallon tub for now.

  2. Pick the options as per your bathing style, i.e., at what water level do you enter the bathtub? – full, 3/4th, or half-filled.

  3. Enter the faucet flow rate. Say 2.5 gallons per minute.

  4. Fill in your weight, this will help estimate the water level rise once you enter the tub. Let's go with 120 pounds (54.43 kg).

  5. The water consumption during a single bath, if you entered the half-filled bathtub is:

    Bathtub water = bathtub capacity × percent full

    Bathtub water = 60 gallons × 50% = 30 gallons

  6. Considering the volume your body displaces in the water to see if some water will overflow the bathtub. Let’s say you weigh 120 pounds.

    Volume displaced = body weight / average human density

    Volume displaced = 120 lb / 8.35 lb/US gallon = 14.37 US gallons

  7. The volume displaced is added to the amount of water in the bathtub to project the bathtub's final water level as 30 gallons + 14.37 gallons = 44.37 gallons.

If you turn off the faucet, once you enter, there's no water wastage or spillage during your bath. However, if you keep it on, the water volume gets added to the above number.

💡 Note: To know your actual shower flow rate, you can work it out using a pitcher and a timer.
You can follow these steps to measure your shower flow rate using a pitcher and a timer:

  1. Choose a pitcher that you know the capacity of. You can use a 1-liter pitcher or 2-liter pitcher for this.
  2. Once you've chosen a pitcher, use your timer to find the time duration it would take to fill your pitcher. Make sure to turn the shower to its maximum to measure the maximum flow rate your shower can give.
  3. Then divide your pitcher's capacity by the duration to fill it with water.

If you chose a 2-liter pitcher, and you filled it with water for 10 seconds, we'll know that its maximum flow rate is 2 L per 10 seconds or 0.2 L/s. You can also do this for your bathtub's faucet to check its actual flow rate.

Who wins – Bath or Shower?

What is more environment-friendly – a shower or a bath? The jury is still out. It all boils down to your habits. On one hand, showers use running water – the longer the shower duration, the more water you will waste.

On the other hand, an average bathtub takes about 25-50 gallons (90-190 liters) of water for single-use. In this case, the gray water, which is the water sitting in the bathtub after you bathe, can be re-used in limited amounts for some other purpose like in flushing toilets, which is not in the case of showers. However, it could be difficult to install a bathtub in case of limited house space. So what is the answer to environment guilt-free showers – a magic number for the duration of showers.

Shower-Bath equivalency
Shower-Bath equivalency

In the above chart, considering a 50-gallon bathtub for comparison with showers running at 2.5 gallons per minute, we found out that a 20-minute shower at full shower power consumes the same amount of water as a 50-gallon (190 liters) bath! 50 gallons of water for a 20-minute shower is still a staggering amount. But now that you know, you can help remedy it! Knowing is only half the battle. To get over the finish line, you need deliberate action.

Six devices to get the most out of your shower

Did you know that you can still save water while using showers? Here are some tips to get the most out of your shower. The most common way to increase shower efficiency is to install efficient devices or tweak your showering techniques.

First, let’s go over the handy devices which can make your showering experience more environmental-friendly.

  1. Installing EPA approved WaterSense labeled products like faucets, showerheads are known to be water efficient. WaterSense labeled products are EPA certified for being about 20% more water-efficient than the average taps, faucets, and showerheads without compromising on the experience. You can also get rebates for the WaterSense products. Find out how here.
Look for watersense label
WaterSense label
  1. Low flow showerhead – The low-flow showerheads can be identified by their volume flow rate of fewer than 2.5 gallons per minute. Switching to low-flow showerheads also saves energy by cutting down on heater usage. Therefore, providing significant savings in terms of both water and energy.
  2. Aerators – You can also add an aerator to shower and faucet outlets, which are found to be water and energy-efficient. An aerator works by drawing air into the water flow, mixing them to create an air-water stream. That stream passes through a screen dividing it into several mini-streams while coming out of the faucet or showerhead. If you have a vivid imagination, you can pretend to be an airplane having to withstand "wind" and rain. Check the crosswind calculator to see what forces you would deal with.
  3. Rain showerhead – A rain showerhead creates multiple water mini streams, maintaining uniform temperature, just like you are drenching in the rain.
  4. Handheld showerhead – A handheld showerhead can give concentrated coverage and quicker shower, therefore saving water and energy.
  5. Flow restrictor – While buying a showerhead, always look for a flow restrictor and a multiple-setting showerhead, so you can adjust the water flow as per your needs.

If you're set on implementing some of these solutions now, the lead time calculator might help you with the timeframe needed to get it done - from the moment of ordering until the part's been installed!

Eight ideas to take an eco-friendly shower or bath

You would be surprised to know that you’re a few tweaks away from an environment-friendly shower and bath. Here’s how:

  1. Turn off the showerhead or reduce the flow using a flow restrictor while you lather.
  2. You can use a shower timer, or maybe sing your favorite song, with your shower lasting one or two songs long to note your shower time.
  3. Scheduled maintenance – cleaning your showerheads for any clogs which can potentially reduce water pressure will enhance your showering experience.
  4. You can also try a submarine shower, just like the sailors do in a submarine. A submarine shower uses water only for 20 seconds with a 10-second step to wet, followed by scrubbing and then rinse for another 10 seconds.
  5. You can reduce water usage by taking shorter showers. As per the graph above, you can save 12.5 gallons of water by cutting down your shower by 5 minutes.
  6. Check for any leaks in your bathtub and perform preventive maintenance.
  7. Fill the bathtub only halfway before stepping into it to avoid any overflow and spillage.
  8. Turn off the faucet once you have adequate water in the bath to avoid overflow.
Kenneth Alambra and Rahul Dhari
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Find out how much water you use while taking a shower 🚿 compared to taking a bath 🛁, and learn how much water you save or waste when choosing one over the other.
Let's see how you can conserve water and help save the Earth in your own little way. 🙂🌍
Compare my water usage on a...
weekly basis
Shower preferences
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Continuous shower
Average shower duration 🕗
Shower power
Full turn
Shower frequency
Total water used for shower 🚿
US gal
Bath preferences
Bathtub size
Standard 180-L (48-gal) tub
I like to bath in a...
fully-filled tub
I get in the bath...
when the water reaches that level
When in the tub,...
I turn off the faucet
Your weight
Bath frequency
Total water used for bath 🛁
US gal
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