Knowing how to read an oil tank gauge is important to knowing how much oil is left – and how much you should order.
This page explains how to read oil tank gauge and gives accurate information on how much oil is left in a 275 gallon horizontal or vertical tank. For other oil tanks from 100-1000 gallons, you can check the charts here.
Tank Gauge Reading
Most 275 gallon heating oil tanks have gauges showing oil level in 1/8 increments – 1/8, 1/4, 3/8, 1/2, 5/8, 3/4 and 7/8. They also show E for empty and F for full.
There is a float inside the gauge tube. It rises or falls with the oil level in the tank. The top of the float shows how full the tank is.
Your gauge should rarely read “F” for Full because tanks are only supposed to be filled to about 90% of capacity to give the oil a little room to expand.
So, a 275-gallon fuel oil tank when considered “full” has about 240 to 250 gallons in it. So, your gauge should read about 7/8 or a little higher when the tank is at the safe capacity.
Heating Oil Tank Gauge Level and Gallons In It
This table does the math for you. Based on the gauge reading, you will know how much heating oil is in the tank and how much to order if you want it at maximum capacity, or about 90%.
275 gallon oil tank gauge chart
| Gauge Level | Current Amount | Amount needed to fill tank |
| 1/8 | 35 gallons | 190-200 gallons |
| 1/4 | 69 gallons | 170-180 gallons |
| 3/8 | 103 gallons | 140-150 gallons |
| 1/2 | 138 gallons | 100-110 gallons |
| 5/8 | 172 gallons | 50-70 gallons |
| 3/4 | 206 gallons | 20-30 gallons |
| 7/8 | 241 gallons | 0 gallons |
How much oil is left when the gauge is 1/4?
69 gallons, give or take a few gallons.
How much oil do I need to fill it with the gauge at 1/4?
170-180 gallons will fill it to safe capacity.
These Q&As show how to read oil tank gauge to know how many gallons are in it and how many are needed to fill it.
Inches to Gallons for 275 Gallon Horizontal Oil Tank
Did you know that you can also measure the oil in the tank to determine how many gallons of heating oil are left?
Use a clean dowel rod or other straight, firm rod such as a 1”x2” board. With the tank cap off, push it straight to the bottom. Pull it out, wiping off the excess oil as it comes, and measure the wet part of the stick.
This chart shows you how much oil is in it based on how many inches are left.
275 oil tank measurement chart (Horizontal)
H/W/L=27”/44”/60”
| Inches | Gallons |
| 1″ | 6 |
| 2″ | 14 |
| 3″ | 22 |
| 4″ | 31 |
| 5″ | 41 |
| 6″ | 52 |
| 7″ | 63 |
| 8″ | 74 |
| 9″ | 85 |
| 10″ | 96 |
| 11″ | 108 |
| 12″ | 119 |
| 13″ | 131 |
| 14″ | 143 |
| 15″ | 154 |
| 16″ | 166 |
| 17″ | 178 |
| 18″ | 189 |
| 19″ | 199 |
| 20″ | 211 |
| 21″ | 222 |
| 22″ | 232 |
| 23″ | 240 |
| 24″ | 251 |
| 25″ | 260 |
| 26″ | 268 |
| 27″ | 275 |
How many gallons left is 12”?
119 gallons, or very close to it. Your tank is about 1/2 full.
12” of oil is left. How much should I order?
About 120 gallons.
Inches to Gallons for 275 Gallon Vertical Oil Tank
The dimensions of a vertical tank are similar but different to a 275 gallon horizontal tank. Basically, the length is the same, but the height and width are switched.
Dimensions are H x W x L:
Horizontal 275-gallon tank dimensions: 27”x44”x60”
Vertical 275-gallon tank dimensions: 44”x27”x60”
275 oil tank measurement chart (vertical)
H/W/L=44”/27”/60”
| Inches | Gallons |
| 1″ | 2 |
| 2″ | 5 |
| 3″ | 9 |
| 4″ | 14 |
| 5″ | 19 |
| 6″ | 25 |
| 7″ | 31 |
| 8″ | 37 |
| 9″ | 44 |
| 10″ | 51 |
| 11″ | 58 |
| 12″ | 65 |
| 13″ | 72 |
| 14″ | 80 |
| 15″ | 87 |
| 16″ | 94 |
| 17″ | 101 |
| 18″ | 108 |
| 19″ | 115 |
| 20″ | 123 |
| 21″ | 130 |
| 22″ | 137 |
| 23″ | 144 |
| 24″ | 151 |
| 25″ | 158 |
| 26″ | 166 |
| 27″ | 173 |
| 28″ | 180 |
| 29″ | 187 |
| 30″ | 194 |
| 31″ | 201 |
| 32″ | 209 |
| 33″ | 216 |
| 34″ | 223 |
| 35″ | 230 |
| 36″ | 236 |
| 37″ | 243 |
| 38″ | 249 |
| 39″ | 254 |
| 40″ | 260 |
| 41″ | 265 |
| 42″ | 269 |
| 43″ | 272 |
| 44″ | 275 |
FAQs
How do you read an oil tank gauge?
There are many different heating oil tank gauge styles. But they are common in two ways:
- They use a float
- The top of the float is what you use to determine how full the tank is
The tank gauge doesn’t move. What’s wrong?
Heating oil tank gauges get old and gummed up with sludge. When that happens, they get “stuck” and won’t move up or down.
My gauge is stuck. What should I do?
First, measure the amount of oil in the tank, so you know how soon you need to order more oil. Then, when you call to order a delivery, let the supplier know that the gauge isn’t working.
Can you suggest a reliable oil tank gauge?
Sure. This Smart Oil Gauge replaces the tank cap and uses ultrasonic technology to read how full your tank is. The gauge is equipped with WiFi, and you can monitor tank fullness from anywhere using the app. The WiFi oil tank gauge also allows you to set reminders at the fullness level you choose for when to order more heating oil.
