Oil burner nozzle chart and fuel use calculator
Every oil burner nozzle is stamped with its rated flow in gallons per hour at 100 PSI. Run the pump at higher pressure, as most modern burners do, and the real flow rises with the square root of the pressure. Know your nozzle, your pressure, and your hours, and you know your gallons without ever seeing the tank.
GPH
gallons
Enter the rated GPH to see your true burn rate. Add hours from a burner hour meter to turn it into gallons.
Nozzle flow chart: rated GPH at real pressures
| Rated GPH | 100 PSI | 125 PSI | 140 PSI | 150 PSI | 175 PSI |
|---|---|---|---|---|---|
| 0.50 | 0.50 | 0.56 | 0.59 | 0.61 | 0.66 |
| 0.60 | 0.60 | 0.67 | 0.71 | 0.73 | 0.79 |
| 0.65 | 0.65 | 0.73 | 0.77 | 0.80 | 0.86 |
| 0.75 | 0.75 | 0.84 | 0.89 | 0.92 | 0.99 |
| 0.85 | 0.85 | 0.95 | 1.01 | 1.04 | 1.12 |
| 1.00 | 1.00 | 1.12 | 1.18 | 1.22 | 1.32 |
| 1.10 | 1.10 | 1.23 | 1.30 | 1.35 | 1.46 |
| 1.20 | 1.20 | 1.34 | 1.42 | 1.47 | 1.59 |
| 1.35 | 1.35 | 1.51 | 1.60 | 1.65 | 1.79 |
| 1.50 | 1.50 | 1.68 | 1.77 | 1.84 | 1.98 |
| 1.65 | 1.65 | 1.84 | 1.95 | 2.02 | 2.18 |
| 1.75 | 1.75 | 1.96 | 2.07 | 2.14 | 2.32 |
| 2.00 | 2.00 | 2.24 | 2.37 | 2.45 | 2.65 |
Computed from the standard nozzle flow relationship: actual GPH equals rated GPH times the square root of pressure over 100. Worn or plugged nozzles drift from these figures, which is one reason nozzles are replaced at every annual tune-up.
Worked example: a 0.85 nozzle at 140 PSI flows 0.85 × √1.4, about 1.01 GPH. Run it 100 hours and the burner has used about 101 gallons.
Pair it with an hour meter
An elapsed-time meter wired across the burner motor turns this math into a fuel gauge for tanks you cannot measure. It is an inexpensive part and a quick job for your tech at a tune-up. From then on: hours since the last fill, times your actual GPH, equals gallons burned, and your tank size minus that is what remains.
Common questions
Where do I find my nozzle size?
On the service sticker or the last tune-up invoice, where techs record it as size, angle, and pattern, for example 0.85 80 B. The stamp is also on the nozzle body itself, but that lives inside the gun assembly; ask your tech rather than pulling it.
What pressure is my burner running?
The old standard was 100 PSI; most modern flame-retention burners run 140 to 150, and some high-pressure setups go higher. The service sticker or your tech knows the set pressure. If you have no information, 140 is the realistic guess for anything installed in recent decades.
Why does my burner use more than the nozzle says?
Because the rating is defined at 100 PSI and your pump probably runs above that. Flow rises with the square root of pressure, so a 1.00 nozzle at 140 PSI really delivers about 1.18 GPH. A worn nozzle drifts higher still.
How does this compare to my gallons-per-day numbers?
They should agree. A 0.85 nozzle at 140 PSI running 5 hours on a cold day is about 5 gallons, right in the typical winter band the days-left calculator uses. When the two disagree badly, the hour meter is usually the honest one.
Related
- Nozzle converter for techs (reverse lookup and a denser printable chart)
- No gauge, no stick: tracking oil anyway
- Heating oil usage calculator
- How long will my oil last?