Work out oil tank duration instantly with clear inputs, formula shown and shareable results.
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.
Burn rate
gal/h = burner input x duty cycle / 138500
Duration
hours = (tank gallons x level - 5 percent reserve) / burn rate
gal/h = burner input x duty cycle / 138500. Number two heating oil holds about 138,500 BTU per gallon.
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.
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.