500 gallon oil tank chart
Dip stick chart for a 500 gallon tank, often buried. Read the dip in inches, find the row, and the gallons are next to it.
Worked out from the outside size listed by oiltankcharts.com and Hillside HVAC. Approximate, and a delivery stops below the top row. https://fuel-tank-chart.tilraunlab.com/500-gallon-oil-tank-chart
500 gallon oil tank chart
A 500 gallon oil tank is a round steel cylinder, 48 in across and about 65 in long. oiltankcharts.com and Hillside HVAC both list those two numbers. This size is often buried in the yard, so the stick goes down a fill pipe or a gauge port rather than through the top of a basement tank. The table below turns each inch of oil on the stick into gallons.
Your reading
This is the geometric volume of the cylinder, in cubic inches divided by 231. The tank is called a 500 because the real figure is rounded down.
Three readings to remember
By my table, 12 in on the stick is 100 gal, 24 in (the halfway point) is 255 gal and 40 in is 453 gal. Seller charts run a little higher or lower, often by 1% to 3%, because most of them round to whole gallons or take the tank as a flat 500. Hillside HVAC lists 98 gal at 12 in and 250 gal at 24 in, and oiltankcharts.com lists 100, 255 and 453 gal at 12, 24 and 40 in. Treat the gap as normal, since real tanks also vary by maker.
Float gauge marks in gallons
The gauge shows F, ¾, ½ and ¼ of the volume. On a round tank the ¼ mark sits at 14.5 in on the stick, higher than a quarter of the 48 in, because the bottom of a circle is narrow.
| Gauge | Gallons | Dip |
|---|---|---|
| Full | 509 | 48.0 in |
| 3/4 | 382 | 33.5 in |
| 1/2 | 255 | 24.0 in |
| 1/4 | 127 | 14.5 in |
| 1/8 | 64 | 8.5 in |
Inches to gallons
| Dip | Gallons | Full |
|---|---|---|
| 0 in | 0.0 | 0.0% |
| 1 in | 2.6 | 0.5% |
| 2 in | 7.3 | 1.4% |
| 3 in | 13.3 | 2.6% |
| 4 in | 20.3 | 4.0% |
| 5 in | 28.1 | 5.5% |
| 6 in | 36.7 | 7.2% |
| 7 in | 46.0 | 9.0% |
| 8 in | 55.8 | 11.0% |
| 9 in | 66.1 | 13.0% |
| 10 in | 76.9 | 15.1% |
| 11 in | 88.0 | 17.3% |
| 12 in | 99.5 | 19.6% |
| 13 in | 111.4 | 21.9% |
| 14 in | 123.5 | 24.3% |
| 15 in | 135.9 | 26.7% |
| 16 in | 148.6 | 29.2% |
| 17 in | 161.4 | 31.7% |
| 18 in | 174.4 | 34.3% |
| 19 in | 187.6 | 36.8% |
| 20 in | 200.8 | 39.4% |
| 21 in | 214.2 | 42.1% |
| 22 in | 227.6 | 44.7% |
| 23 in | 241.1 | 47.3% |
| 24 in | 254.6 | 50.0% |
| 25 in | 268.1 | 52.7% |
| 26 in | 281.6 | 55.3% |
| 27 in | 295.0 | 57.9% |
| 28 in | 308.4 | 60.6% |
| 29 in | 321.6 | 63.2% |
| 30 in | 334.8 | 65.7% |
| 31 in | 347.8 | 68.3% |
| 32 in | 360.6 | 70.8% |
| 33 in | 373.2 | 73.3% |
| 34 in | 385.6 | 75.7% |
| 35 in | 397.8 | 78.1% |
| 36 in | 409.6 | 80.4% |
| 37 in | 421.2 | 82.7% |
| 38 in | 432.3 | 84.9% |
| 39 in | 443.1 | 87.0% |
| 40 in | 453.4 | 89.0% |
| 41 in | 463.2 | 91.0% |
| 42 in | 472.4 | 92.8% |
| 43 in | 481.0 | 94.5% |
| 44 in | 488.9 | 96.0% |
| 45 in | 495.9 | 97.4% |
| 46 in | 501.9 | 98.6% |
| 47 in | 506.6 | 99.5% |
| 48 in | 509.2 | 100.0% |
500 gallon or 550 gallon: which one do you have?
The two tanks look alike and have the same 48 in diameter, so they share a half-full dip of 24 in. They differ in length. The 500 is about 65 in long and the 550 about 72 in, so a 550 holds roughly 55 gal more when full and 27 gal more at 24 in. Using the 550 chart on a 500 tank overstates your oil. Measure the length along the shell, or read the data plate. If you can only see the fill pipe, ask the company that delivers. The calculator takes any length.
How full a delivery fills it
Hillside HVAC says the 500 gallon cylinder "is usually filled to about 450 gallons". In my table that is a stick reading of about 40 in (453 gal). Ninety percent of the full volume would be a reading near 40.5 in. Your supplier decides the real limit, so a stick above 40 in leaves little room for a delivery.
Worked example: when to call
A reading of 10 in is 77 gal (15% of the full volume). Keeping a 10% reserve (51 gal, my own choice) leaves 26 gal. A house burning 4 gal a day (an example) has 6 days. Your own rate comes from two dips a week or two apart, as the run-out guide explains, and the 500 preset with a 10 in reading is already filled in.
Other sizes: the 330 gallon chart, the 550 gallon chart and the 1000 gallon chart. To see how much one inch is worth on each tank, use gallons per inch.