Estimating pool size


Well-known member
Aug 5, 2015
Central NJ
I've always used "30k gal" as our pool size, but I don't actually have any idea where I got that from. I can't find it in any legacy records (we have the original paperwork from when the pool was installed 20+ yrs ago) or our pool inspection when we moved in last year. I tried using the details I do have with PoolMath, but I'm not sure I'm doing it right. I'm getting 50k gal which is pretty different! It's a freeform pool which makes it a bit more confusing. These are the dimensions I have. Any help?
View attachment 51393


LifeTime Supporter
Some of the math wizards will be able to help get it close. For a ballpark range though I used FC and pool math. I tested FC with the 25ml sample. Added a known amount of bleach and tested again after it was mixed. I put those in as current and target, then changed the pool volume up above until the recommended amount matched what I actually put in.


LifeTime Supporter
Aug 18, 2014
Amelia Island, FL
50,000 might not be far off, but it's very difficult for any of us to know on a free form pool without more information. For example, how is the pool shaped? Is there more area in the deep end or shallow end? What is the approximate slope?

Do you have plans that show the size/depths of different areas? When you built the pool, did you happen to have a metered fill on your water bill?


TFP Expert
LifeTime Supporter
Jan 4, 2016
Sydney, NSW, Australia
Pool Size
Salt Water Generator
Try 35,000 gallons in PoolMath and the method Scott explained above. If you do it when the pool is sparkly clean and the sun is off the pool, it works.

Also, regular use of PoolMath and recording predicted change vs. actual change, you should be over-shooting and under-shooting about the same amount. If constantly under-shooting the predicted change, lower your pool volume a bit in PoolMath until results get close most of the time.