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Oil Tank Duration Calculator

Work out oil tank duration instantly with clear inputs, formula shown and shareable results.

About Oil Tank Duration Calculator

Number two heating oil holds about 138,500 BTU per gallon. Burner input times duty cycle gives the hourly draw, and the tank contents less a five percent unusable bottom allowance gives what can actually be burned before sludge and water are drawn into the line.

Formulas

Burn rate

gal/h = burner input x duty cycle / 138500

Duration

hours = (tank gallons x level - 5 percent reserve) / burn rate

Worked example

With the default values below, Oil Tank Duration Calculator returns Burner hours remaining of 598.5. Change any input above and every figure here is recalculated in your browser.

Inputs used

Tank capacityminimum 1 gal
275 gal
Current levelaccepts 1–100 %
60 %
Burner input ratingminimum 1 BTU/h
100,000 BTU/h
Average duty cycleaccepts 1–100 %
35 %

Results

Burner hours remaining
598.5 h
Days of supply
24.9 days
Usable oil
151.3 gal
Average daily use
6.06 gal/day

Step by step

  1. 1Values used
  2. 2Burn rate
  3. 3Duration
  4. 4Burner hours remaining= 598.5 h
  5. 5Days of supply= 24.9 days
  6. 6Usable oil= 151.3 gal
  7. 7Average daily use= 6.06 gal/day

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Oil Tank Duration figure worked out?

gal/h = burner input x duty cycle / 138500. Number two heating oil holds about 138,500 BTU per gallon.

Why leave a reserve at the bottom?

Water and sediment collect below the suction line. Running a tank near empty pulls that debris into the filter and nozzle and is the most common cause of a no-heat call.

What values do I need to enter?

This calculator takes 4 inputs: Tank capacity, Current level, Burner input rating, Average duty cycle. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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