Filter tank replacement

Hello,

My sand filter tank has developed a few hairline cracks and needs to be replaced. Unfortunately, I have no way to determine the size tank I currently have. All of the labels have eroded over time and I have no way to find model numbers, much less the manufacturer (I believe it is a Hayward). I see that the replacement tanks come in many different measurements. Any way for me to measure my current tank to find the replacement tank I need to order? I would like to keeps current size due to not wanting to change any plumbing.

Any help would be greatly appreciated and if anymore information is needed I will gladly supply ASAP.

Thanks,

Richey