One of the most common sizes of home heating oil tanks is 275 gallons. These are typically the oval tanks with two flat ends, standing on four short steel legs. Knowing how much oil is in the tank assures you have a steady source of heat during the cold winter months. A mechanical float-style gauge is used to approximate the volume of oil in the tank. It is wise to have it filled when it reaches the 1/4 reading.
Locate the oil tank. It is typically on the exterior of the home, on the same side as the HVAC equipment installed in the basement. It can also be located in the basement of the house. If it is in neither location, it may be buried in the yard.
Find the gauge on top of the tank. It looks like an inverted small, glass jar with a measurement indicator inside.
Look to see where the gauge's indicator lines up with measurements printed on the glass of the gauge. Typical measurements are: F = full, 3/4 full, 1/2 full, 1/4 full and 0 = empty.