FuelMetric ProCalculation method
How FuelMetric Pro turns a dip, a temperature and a density into a quantity in metric tons. The same steps are listed in the app under Settings › About › Calculation method.
Standard
ASTM D1250-80 (API 2540), Petroleum Measurement Tables: Table 53B for the density at 15 °C and Table 54B for the volume correction factor (VCF), for generalized products in the fuel-oil range. Values follow the printed ASTM D1250-80 tables.
Steps and rounding
| Step | Rule |
|---|---|
| Temperature | The nearest 0.25 °C table row is used. A reading that is not on a 0.25 °C step gets a warning: the Standard does not intend interpolation on temperature. |
| Density at 15 °C (Table 53B) | Linear interpolation on density between the two table columns, on the temperature row used, rounded half-up to 0.1 kg/m³. Shown in g/cm³ to 4 decimals. |
| VCF (Table 54B) | Nearest even density column (an exact half goes to the lower column), no interpolation. VCF to 4 decimals. |
| Observed volume | From the tank's calibration chart: exact chart rows, the fraction table (1 to 9 mm) where supplied, otherwise linear interpolation between rows. Dips outside the chart are refused. |
| Net volume at 15 °C | Observed volume × VCF, rounded to whole litres. |
| WCF | Density at 15 °C (g/cm³) − WCF offset. The offset is 0.0011 unless set otherwise for the site. |
| Quantity | Net volume × WCF ÷ 1000, in metric tons to 3 decimals. |
| Stock | Usable stock = total stock − dead stock, never below zero. A tank without a dip on a day keeps its last reading. |
Worked example
One tank, as entered in the app: dip 7,460 mm, temperature 48.50 °C, observed density 972.4 kg/m³.
| Value | Result | How |
|---|---|---|
| Observed volume | 2,343,634 L | Tank chart at 7,460 mm |
| Density at 15 °C | 994.4 kg/m³ | Table 53B, row 48.50 °C |
| VCF | 0.9771 | Table 54B, row 48.50 °C, column 994 |
| Net volume at 15 °C | 2,289,965 L | 2,343,634 × 0.9771 |
| WCF | 0.9933 | 0.9944 − 0.0011 |
| Quantity | 2,274.622 MT | 2,289,965 × 0.9933 ÷ 1000 |
Limits
Observed density 800 to 1075 kg/m³ and temperature −18 to 150 °C. A density at 15 °C below 839 kg/m³ is outside the fuel-oil range, and above 120 °C is the extrapolated region of the tables. Light products such as petrol use other constants and are not covered.
Checking the numbers
Every report lists the values used for each tank: dip, temperature, observed density, density at 15 °C, VCF, observed and net volume and WCF, so a reviewer can check any line against the printed tables. Results depend on the charts and readings entered; check important figures against your official documents and procedures.
FuelMetric Pro is an independent app and is not affiliated with or endorsed by ASTM International, API or the Energy Institute.