Bathroom membrane calculator

Answers the question: How much liquid bathroom membrane do I need?

This bathroom waterproofing membrane calculator helps you calculate how much liquid waterproofing membrane you need when building a bathroom. This calculator estimates the total liters of membrane required to cover both walls and floor. The calculator will deduct the size of doors and windows as you don't need to put membrane there.


Total membrane area: 68.08 square meters
Liters of membrane needed: 52.37 liters
Number of membrane buckets needed: 4

This waterproofing membrane calculation is an estimation. We recommend adjusting for some waste. Generally, we recommend two layers of liquid membrane for any wet room, but you should always follow the membrane manufacturer's instructions.

Our calculations

At Calculatorian, we are keen to share our knowledge, be transparent and open to feedback. Here are the calculations used to create this calculator. If you find an error or deficiency, contact us and we'll fix it in an instant!

Total membrane area was calculated like this:

Step 1

First we need to calculate the variable da. da = door area in square meters.

Step 2

Then we need to calculate the variable wa. wa = window area in square meters.

Step 3

Finally we put it together and calculate it like this:

Liters of membrane needed was calculated like this:

Number of membrane buckets needed was calculated like this:

Variables used in this formula

l = Room length in meters
w = Room width in meters
h = Wall height in meters
d = Number of doors
wg = Number of windows
c = Square meters that one liter of membrane cover
pb = Liters per bucket of membrane
la = Number of membrane layers