Wednesday, May 6, 2009

Calculate Aquarium Thickness - How THICK must the Plexiglas be?

To determine the proper thickness for an aquarium made of ACRYLITE® GP acrylic sheet...
OK - this is for all you Einsteins out there - even if it's high school physics and math... please don't ask me the calculate this.. :-) - check out the Cyro Tech-Knowlogy site for a spreadsheet to help. You have to login in - but it is a killer info site.
The aqaurium in the picture is 12ft long, 4ft high and about 3ft wide in the middle. It was constructed of 2" thick acrylic sheet, the outer walls were thermoformed into convex sheets, and please note the "top cap" made of 1" thick plexiglas sheet, then routed out for access holes. This top cap also creates a structural member that keeps the outer walls from bulging under pressure. This aquarium is now doing service in upstate Michigan.
CYRO recommends that all acrylic water vessels, including aquariums, should be constructed with cell cast ACRYLITE GP sheet. This requirement exists for two reasons:
  1. ACRYLITE GP sheet is more capable of withstanding continuous loads than continuously manufactured or extruded sheet.
  2. ACRYLITE GP sheet maintains a high level of mechanical strength after water absorption has reached equilibrium.
Cemented joints must withstand the effects of the continuous hydraulic pressure and the high level of water absorption for many years. Two-part polymerizable cements are recommended for this to meet this requirement. See Weld-On #40 information in the blog. Solvent cements are NOT recommended.
To determine what thickness acrylic sheet should be used, the calculation below can be used assuming the base is uniformly supported.

T - thickness of sheet
H - height of tank
L - length of tank
Required Thickness T (in)=           
q = maximum water pressure (lbs/in.2) = (0.0361 lbs water/in3)* H (inches)
H = aquarium height (inches)
α = maximum permissible stress for ACRYLITE GP in an aquarium (750 psi)
β = coefficient from L/H relationship as follows:
L/H 0.25 0.50 0.75 1.00 1.50 2.00 3.00 4.00
β 0.037 0.120 0.212 0.321 0.523 0.677 0.866 0.940
Note: For L/H ratios not shown, use the β value for the next higher ratio.
L = 36 in.
H = 15 in.
L/H = 2.4 therefore: b = 0.866 (taken from the chart for L/H = 3.0)
q = (0.0361 lbs/in3) x (15 in) = 0.542 lbs/in2

T (in) =

= 0.375 inches

If a top is cemented on (this would have 2 cutouts to prevent bowing), the recommended thickness in 0.375 inches. With an open top use a safety factor of 1.5, bringing the recommended thickness to 0.563 inches to be used in this size tank. Since a thickness of 0.563 is not made, simply increase this to 0.740" (3/4") which is stock.
OK - did I blow your mind? WWPGD? If you want to build an aquarium, and the edges are hidden by framework, or the mounting in a wall, etc. then use 1/2" CAST ACRYLIC SHEET for aquariums that are 15" high x 20" wide x 36" long. Make sure there is a top cap to keep sides from bulging. 24" x 24" x 48" - use 3/4" sheet and 30"x30"x48" use 1" sheet. Always use a top cap sheet to hold side together!
If you are not skilled with gluing Plexiglas, search out a local plexiglass fabricator in your area. Typically under the Yellow Page heading of Plastics - Fabricators. If the edges are showing, make sure the fabricator defines how bubble-free their bonds will be and the quality of the edge polishing. Expect to place a 50% deposit on the order and the balance when complete to your satisfaction. To save money, identify what edges do NOT need to be polished - that saves time and your money!

Thanks to

Download the XLS from Evonik - Calculate Aquarium Thickness  


  1. Welcome!
    Please help me:
    I am beginner aquarium builder.
    Please send me one table of acrylic thickness for aquarium heights.
    The acrylic stronger than glass - write the Acrilyc catalog...
    But the acrylic calculators calculate biggest thickness, than a glass calculator.
    Aquarium heights: 50 inch:Results:
    Glass calc.: 1,27 inch
    Acrylic calc: 2,28 inch thickness
    What is a justice data? Or the glass stronger than acrylic?
    Thanks, and best regards:
    Sándor Iványi
    Hungary, Europe:

  2. I can´t see the pictures.

    T (in) = ???? = 0.375 inches

    Send me please your e-mail. I have a project to talk to you.

  3. where can i purchase 6 10'x10'x2.25" polycarbonate

  4. I need a human dunk tank 8ft high and 6 ft long. It is for a photographer located in Michigan. Please contact me or by phone 19895985418
    Thanks, Seth Ortega

  5. I don't have an aquarium to build but I'm a fashion photographer looking to build a platform with a transparent top to support an adult female. I need it to be approximately 6' long and about 3.5' wide. Any recommendations?


  6. Thank you man! that's so useful. appreciate!
    what about a cylinder? how can i calculate proper thickness for cylinder?

  7. Thank you for your post! it is very informative.
    I have one other question. I figured out where this equation comes from, but still not sure where this table with L/H ratios and Beta values come from.. Could you please post the source as well? Is Beta dependent on the material?

  8. Artur, right click (or control click on a Mac) and "save link as" to download the Excel file. Plug in you length and height and voila!

  9. Thanks, that has worked pretty well for me. What do I do if I decide to use different material? Can I still rely on this method and assumptions?

  10. could someone please direct me to an online calculator to derive the thickness of acrylic sheet required for vertical aquariums? would much appreciate....thankyou.....

    1. Hello Peter.

      We have not created one of these by ePlastics® since the materials change based on the manufacturer. With that, I would recommend clicking on the Cyro link below and registering with them for access to their calculator.

      If you have additional questions, feel free to get some assistance from our staff by calling 1-800-474-3688.

  11. I am an aquatic supervisor. We are building swim platform to put in the water so that 4- 6 children can stand on it during swim lessons. We are building the frame out of pvc pipes but I am unsure on what to use for the platform floor. It should be waterproof lightweight and capable of supporting 200 - 300 lbs. or 6 kindergardeners jumping on it. ( in the water). What would you suggest?

    1. For this application you will definitely want to use polycarbonate sheet.

      I cannot recommend a thickness confidently without all of the product details, however from the information you provided here it sounds like 0.250” thick material should work well.

      Remember that when fabricating, you will need special saw blades and drill bits in order to keep the material from breaking. If you have any more questions about this unique application, feel free to add them here or email them directly to

  12. How thick do you recommend for a tank 25 foot long 18 inches wide and 20 inches tall

    1. You have a long shallow tank. Nonetheless there is pressure and a minimum of 2” thickness sides with 1.50” bottom is required.