How Long Does it Take to Fill an Average Bathtub?

The bathroom is the most serious consumer of water in our house, and taking a shower or a bath takes the first place on that list. But regardless of that, if we want to take a bath, how much time it will take us to fully fill a bathtub? Keep in mind that there are no standard bathtub sizes on the market. Let’s find out!

How Long Does it Take to Fill an Average Bathtub?

How Long Does it Take to Fill the Average Bathtub? It takes around 5 to 10 minutes for an average bathtub to fill. Things that depend on how fast the bathtub will be filled up are the size of the tub, water pressure, and the size of pipes from where water leaks into the tub.

Table: the time it takes to fill the different sizes of bathtubs.

Bathtub Volume:Filling Time:Flow Rate (m3/s):Type:
1. 30 Gallons (113 liters)5 minutes4 to 7 gpm (lpm)XSmall
2. 40 Gallons (151 liters)6.5 minutes4 to 7 gpm (lpm)Small
3. 60 Gallons (227 liters)10 minutes4 to 7 gpm (lpm)Medium
4. 80 Gallons (302 liters)13 minutes4 to 7 gpm (lpm)Large
5. 100 Gallons (378 liters)16.5 minutes4 to 7 gpm (lpm)XLarge
Different bathtub sizes and time it takes to fill it; gpm – gallons per minute

If it takes a lot more time than this to fill the bathtub, call a licensed plumber to see what the problem is.

The average tub faucets run at approximately 4 to 7 gallons per minute while the average bathtub has a volume of approximately 40 to 60 gallons. So it takes around 5 to 10 minutes on average to fill the bathtub. The table above shows the most common bathtub sizes and the time it takes to fill.

To precisely measure the time, use one of these stopwatches.

How to Calculate Time it Takes to Fill the Bathtub?

The volume of any bathtub can be measured by a mathematical formula. Therefore, to measure the volume of the bath we need parameters such as; height or depth of the bowl, bath length, and the width of the bowl. This formula will give us an approximate result since accurate measurements go into the field of integral calculus. The average person will lose interest in this issue if they do not use a simplified formula.

Formula for Bathtub Volume is:       V = H * L * S 

V – is the required volume,

H – is the height or depth of the bowl,

L – bath length,

S – the width of the bowl

Formula for Time it Takes to Fill the Bathtub: T = V * F

  • F – 4 to 7 Gallons per minute (we take 6 gpm)

Sometimes the bathtubs are designed a little differently so the calculation of the volume of spherical models is different. Therefore, we will give an example of these models as well. Use the calculator for this.

To calculate Volume of this Bathtub you need to use number π

In that cases, you need to use number π (which is = 3.14), because first, you need to calculate the area of a semicircle, and then multiply by the length or depth (depending on the specific shape), then the formula may change: 

V = π * H * L * S.

What If it Takes Longer Than 10 Minutes To Fill?

If you have the standard bathtub that can hold approximately 60 to 70 gallons of water, it shouldn’t need more than 10 minutes to fill it. Therefore, if you need more than 20 minutes to fill the volume of a bathtub that has 60 to 70 gallons of water then the problem is in the very small tap diameter or you have slow water pressure.

In that case, it is best to contact a plumber and see what can be done about it. If the problem is only in the faucet, it can be easily replaced. If the problem is low pressure, then the plumber must address the problem in detail. For bathtubs that can hold around 100 gallons of water take about 20 minutes to charge.

Also, if you are interested on How a Bathtub Works, check out this article.

How Long it Takes to Drain Water From a Bathtub?

For an average bathtub to drain its water it takes typically around 4 to 6 minutes if the existing drain system operate properly. Factors that depend on how quickly the water will drain from the bathtub depends on the volume of the tub, the filling of the tub, and the diameter of the drain. The standard bathtub drain is around 1 ½ inches in diameter. Such a drain diameter can easily accommodate around 8.5 gpm (gallons per minute). If the water is drained very slowly from your bathtub, the problem is most likely a clog that is restricting water flow.

For those who want to know more, you can read What Is A Safe Bath Water Temperature? Dermatologist Explain

How Much Water Does a Bathtub Faucet Use Per Minute?

The bathtub faucet on average runs at 4 to 7 gallons per minute (15-26 liters per minute). Keep in mind that taking a bath in most cases requires less water than taking a shower. People on average use around 35 gallons of water for a bath, while for showering they sometimes consume 40 gallons of water.

How Many Gallons of Water it Takes to Fill the Bathtub?

The standard bathtub on average can hold around 60 gallons (227 liters) of water if it is fully filled (just below the overflow). The smaller bathtubs that are suited for children can hold around 40 gallons (151 liters) of water. So, according to the industry standards, it takes on average of 35 gallons (132 liters)  of water for a bath.

Final Thoughts

Each bathtub model is designed differently, and their volume varies as we have seen. Therefore, filling the bathtub depends on a lot of parameters that need to be taken into account. Most family bathtubs have a volume of 80 gallons and it takes a little less than 10 minutes to fill it up. We hope that everything is clear to you now and that we have answered the question that you came for.


I'm the CEO and founder of Home Hacks DIY. I have been involved in home improvement since my early age. I will try to pass you my knowledge and expertise in this industry in which I have been involved for the last 10 years.

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