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You are here: Home / Blog / Aquarium Calculator: How Many Gallons Can Your Tank Hold?

Aquarium Calculator: How Many Gallons Can Your Tank Hold?

Last Updated on October 29, 2020 by Ian Sterling 37 Comments

Woman using aquarium volume calculator to find how much water her fish tank will hold

Want to know how much water your aquarium can hold?

Use our handy calculator to find out just how many gallons (or liters) of water your aquarium is capable of holding.

Fish tank volume

How to find the water capacity of your fish tank
  • The distance across the front of your aquarium
  • The distance from the top to the bottom of your aquarium.
  • The distance from the front to the back of your aquarium
  • This is a small tank... So small in fact that it is unsuitable for most fish!

    These tanks and bowls are often sold at bulk retailers by "experts" who will claim they are more than suitable for a single betta (they aren't)

    Believe it or not, these small aquariums are actually the most difficult to keep and are unsuitable for beginners - good filtration is essential!

    I recommend that any fish tank that is less than 10 gallons should only be considered by experienced aquarists who understand the risks and shortcomings of these tiny tanks, as well as how to overcome them.

  • This is a small tank... So small in fact that it is unsuitable for most fish!

    These tanks and bowls are often sold at bulk retailers by "experts" who will claim they are more than suitable for a single betta (they aren't)

    Believe it or not, these small aquariums are actually the most difficult to keep and are unsuitable for beginners - good filtration is essential!

    I recommend that any fish tank that is less than 40 Liters should only be considered by experienced aquarists who understand the risks and shortcomings of these tiny tanks, as well as how to overcome them.

  • This is a mid-sized tank...

    Perfect for beginners. Not so small that water quality is difficult to maintain but not so large that cleaning is a big hassle.

    These tanks are large enough to house a wide range of fish, provided you are careful to research compatible fish that won't outgrow your tank.

    30 - 75 gallons - This is a great starting size for a good marine or salt water tank.

  • This is a Mid-sized tank...

    Perfect for beginners. Not so small that water quality is difficult to maintain but not so large that cleaning is a big hassle.

    These tanks are large enough to house a wide range of fish, provided you are careful to research compatible fish that won't outgrow your tank.

    110 -280 Liters - This is a great starting size for a good marine or salt water tank.

  • This is a large tank...

    A tank this size can stock a wide variety of fish, plants, corals or decorations. You also can't deny that large tanks look stunning.

    While that is undeniably appealing, you will need to work harder to clean and maintain this sized tank.

    You should also note that, when filled with water, a tank of this size is incredibly heavy and you will need to make sure that your cabinet or floor can handle the load.

  • This is a large tank...

    A tank this size can stock a wide variety of fish, plants, corals or decorations. You also can't deny that large tanks look stunning.

    While that is undeniably appealing, you will need to work harder to clean and maintain this sized tank.

    You should also note that, when filled with water, a tank of this size is incredibly heavy and you will need to make sure that your cabinet or floor can handle the load.

Notes on Aquarium Capacity:

Now that you know the volume of water that your aquarium can hold, you will want to be mindful of one fact:

Your aquarium will never actually hold this much water.

For instance, I have never met anyone who fills their aquarium all the way to the top of the tank. Any gap that you leave here will mean that there is less water in your tank.

Also, anything that you place in your tank will remove the same amount of water. Fish, rocks, coral, substrate, decorations… These all mean that there is less water in your tank.

Think of it as though you are filling your bath to the top with water and sliding in – the water is going to overflow because your body is taking up space where the water previously was.

I hope this was helpful. Even if you’re only buying betta, it’s a good idea to calculate how much water you’ll need for its fish tank.

Related posts:

What the Heck Is the Aquarium Water Column?
Surface Agitation: Stir, Churn and Oxygenate Your Aquarium!
What the Heck Is Bioload and Why Is It Important to Your Aquarium?
Ian Sterling
Ian Sterling
I've been keeping fish for over 30 years and currently have 4 different aquariums – it's an addiction. I'm here to teach you everything there is to know about fishkeeping.

I also use this site as an excuse to spend lots of money on testing and reviewing different aquarium products! You can find my reviews here.

Comments

  1. Rick says

    April 3, 2020 at 6:28 am

    What calculator? I don’t see any calculator. Am I supposed to click on something to generate on?

    Reply
    • Ian Sterling says

      April 7, 2020 at 4:52 pm

      Hi Rick,

      It’s loading fine for me. Have you tried using a different browser?

      Reply
  2. joim says

    November 5, 2019 at 1:01 pm

    Your calculator is very wrong using inch to l

    Reply
    • Ian Sterling says

      November 6, 2019 at 3:29 am

      Thank You Joim, I’ll look into this!

      Reply
  3. Eli Ford says

    September 26, 2019 at 4:57 am

    Any idea on places to buy larger 100+ gallon tanks?

    Reply
    • Ian Sterling says

      September 26, 2019 at 7:13 am

      Hi Eli,

      Good question. Once you get to this size, have determined it’s in your price range and don’t want to build one yourself, your best bet is to reach out to a local aquarium manufacturer.

      Going local (if possible) will save on freight as it can be expensive to ship tanks of this size across the country. However, depending on where you are located, this may not be possible. In this case, reach out to a site like glasscages

      Also, at this price range, it may not be more expensive to customize the shape of the tank – this way you can be sure that it fits your living arrangements perfectly.

      Reply
  4. Douglas McMillan says

    September 7, 2019 at 1:29 am

    Thank you. I have been thinking of updating my tank but I have to take into consideration the size of the tank. I have had my present 36 gal tank for over 20 years.

    Reply
  5. Lorrie says

    July 3, 2019 at 9:51 pm

    Thank you for confirming gallon size of my bow front. I bought off Craig’s list and now have to look for a stand. It seems 40 g bow front stands are hard to come by without paying a fortune, if indeed I can find one. Thanks again for your help

    Reply
  6. jenifor barbour says

    July 1, 2019 at 6:39 am

    Thank u so very much for ur site. I have been buying tanks from my yard sale on line because they are more affordable for me but i also like different shaped or size tanks. i bought two tanks that i really liked but didnt no the gallons until now. i have a 58 gal tank. 25x18x30 thank you again for this site

    Reply
    • Ian Sterling says

      July 1, 2019 at 7:23 am

      Hi Jenifor,

      I’m glad I could help. For cheap tanks, I highly recommend keeping an eye out for Petcos dollar per gallon sale, they happen regularly and you can pick up some good aquariums at a budget price.

      Reply
  7. Barbie says

    June 20, 2019 at 6:56 am

    Im trying to set up a 32 gallon water tank for 2 hatchling size turtles i dont know where to start or what to buy

    Reply
    • Ian Sterling says

      June 21, 2019 at 4:45 am

      Hi Barbie,

      Your best bet would be to head to your local fish store (not a big box chain like petsmart or petco) and ask them, exactly what you need will vary according to where you are setting up and a whole host of other factors – you’ll get the best advice there.

      Reply
  8. Jiec says

    June 10, 2019 at 6:02 pm

    How many watts needed for a heater for a 12 x 15 x 36 inches aquarium?

    Reply
    • Ian Sterling says

      June 11, 2019 at 4:03 am

      Hi Jiec,

      It depends on the temperature outside the tank vs. The temperature you want your tank raised to. The difference here in conjunction with the size of your tank is what determines the size of the heater needed in watts.

      Reply
  9. Ray Maier says

    June 5, 2019 at 10:31 am

    Thank you for help , I bought a tank from a friend that is 36”wide by 24” high by 12”deep. Your quick calculating system is great!! Thanks again for your help.

    Reply
  10. Oscar lemence says

    April 11, 2019 at 10:00 am

    Hi!
    Any suggestions on what kind of fish food that will not cloud the water…
    I had 12”x21”x60” aquarium…
    My fish is butterfly koi and goldfish…

    Reply
    • Ian Sterling says

      April 11, 2019 at 12:15 pm

      Hi Oscar,

      It’s unlikely that the fish food is the problem. It’s your stocking. You have too many fish for your aquarium. Read up on ALL the basics, like cycling your aquarium, how many fish can fit etc.

      Reply
  11. Rob Hopkins says

    April 3, 2019 at 6:28 pm

    I would like to use a tank that is set in angle iron frame, the tank measures 183cmX61cmX61cm, I can obtain 6mm glass. And do I need to put Kaolite (a sheet of expanded soft material) at the base, as it has a 2mm iron sheet at the base, welded in place.
    Your advice would be most appreciated.

    Reply
    • Ian Sterling says

      April 4, 2019 at 4:26 am

      Hi Rob,

      Unfortunately, I don’t give construction advice via my blog. I highly recommend joining an online forum, where you can discuss the pros and cons of such a design.

      Reply
  12. Mike says

    March 23, 2019 at 4:41 am

    I purchased a tank used he told me it was 120 g when I looked at it seemed larger I measured it The measurment was 24 “×24″ ×60” so aprox
    150 g and how much did it weigh had to bring it out to the truck then down to twisting steps
    Either 270 lbs or 330 I have to figure out how to move it onto the bar top my self My brother inlaws will not move it again I suppose I will Mcguiver it 1

    Reply
  13. Danny Ryan says

    February 26, 2019 at 11:24 pm

    thanks very much for being here!

    Reply
    • Ian Sterling says

      February 27, 2019 at 6:39 am

      Thanks very much for this calculator!

      Reply
  14. Donald L Martin III says

    January 14, 2019 at 2:38 am

    Thank you.

    Reply
  15. bill says

    October 21, 2018 at 5:24 am

    I find it hard to believe that a 20x20x20 tank in cm is the same size as a 20x20x20 tank in inches. Please explain

    Reply
    • Ian Sterling says

      October 21, 2018 at 6:50 am

      Hi Bill,

      You are correct. It looks like something has gone wrong with the calculator. I’ll have my developer fix it up ASAP. For now the inches to gallons is working correctly.

      Reply
  16. Satya Rao says

    September 8, 2018 at 9:54 am

    Easy to calculate got 5 feet length and 2 feet depth and 2 feet width fish tank. Before loading with accessories wanted to know the gallons or litres of tank. Above calculator was a great help To identify

    Reply
    • Ian Sterling says

      September 8, 2018 at 11:12 am

      Hi Satya,

      Thanks for the feedback. I’m glad you found this helpful!

      Reply
    • Niño Joseph says

      June 27, 2019 at 2:26 pm

      Hello sir,

      My brother and I are setting up a 5 feet in length, 2 feet depth and 2 feet width aquarium which we will only place 1 silver aroana. My brother said he will only use a filter and he was wondering how strong the filter is. The Watts?

      Reply
      • Ian Sterling says

        June 28, 2019 at 6:33 am

        Hi Niño Joseph, most filters give their output in flow rate, e.g gallons per hour.

        Reply
  17. michael says

    August 28, 2018 at 10:33 am

    Does it include the sump pump? When I add chemicals do I add based on the display tank only or whole system?

    Reply
    • Ian Sterling says

      August 28, 2018 at 10:40 am

      Hi Miachael,

      For chemicals such as water conditioner, yes the sump is included. Let’s say you had a 100 gallon display tank and a 30 gallon sump. You would use 130 gallons when figuring out your dosage. Obviously this does not take into consideration any water displaced by decorations, rocks, driftwood, corals etc, so the reality is that the actual amount of water in your tank is less. As always, make sure you follow the instructions carefully when adding any chemical into your tank.

      Reply
  18. Jane says

    August 26, 2018 at 8:53 pm

    I have a 4 foot juwel tank how many gallons dose it hold please

    Reply
    • Ian Sterling says

      August 27, 2018 at 2:57 am

      Hi Jane,

      All you have to do is measure your aquarium and the calculator above will do the rest. A single dimension isn’t enough for me to give you an answer as to how much water your tank can hold.

      Reply
  19. Rhett says

    July 29, 2018 at 1:12 am

    Works good. 55 gallons is what my tank holds.

    Reply
    • FishLab Staff says

      July 29, 2018 at 7:01 am

      Hi Rhett,

      Glad we could help!

      Reply
  20. Nemo Percula says

    July 26, 2018 at 5:16 am

    Great calculator. Exactly what I was looking for. I was buying a new tank this weekend and now I know the water amount in the tank.

    Reply
    • FishLab Staff says

      July 26, 2018 at 5:22 am

      Hi Nemo,

      Glad we could help!

      Reply

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