Boilers - Steam and Hot Water Systems - Determing my tank size

How do I determine the size (in gallons) of my fuel oil tank?

It's 3'9'' high (with a rounded top) x 5' long x 2'3'' deep.

Basically, I think I got ripped off on my last fuel delivery and I'm not sure of the size of my tank. I was told it was 200 gallons, but I'm not sure.

That is a 275 gallon tank.

One thing to keep in mind is that they will never fill the tank much past about 90% full either... so if the tank is completely empty, don't expect much more than say 225-250 gall delivery.

Assuming the bottom is rounded as is the top your tank would have an ultimate capacity of 274.95 gallons. Maximum safe level of 95% would be 261.21 gallons. All US gallons.

How to figure: Convert all dimensions to inches for ease of calculation. Take the width (what you called depth) and consider that the diameter of the top and bottom semi-circular areas when joined to make a circle. Square the diameter and multiply by 0.7854 to get the area in square inches and then multiply by the length to get volume in cubic inches.

27 (diameter) x 27 x 0.7854 = 729.00 square inches x 60 (length)=34,353.4 cubic inches.

Now subtract the diameter from the overall height to get the height of the rectangular portion of the tank. Multiply the height, width and length to obtain the volume of the rectangular portion.

45 (overall height) - 27 (diameter of curved portions) =18 x 27 (width) x 60 (length) = 29,160 cubic inches

Add the two volumes (34,353.4 + 29,161.0 = 63,513.4) and then divide by 231 (the number of cubic inches in a US gallon) = 274.95 US gallons.

All the calculations are nice but there is a vent alarm whistle which has a stem that sticks down anywhere from 2 - 4". So as Trooper said 90 - 95% full.