Calculation methods

VCFAPI returns the Volume Correction Factor (VCF) using the density-based correction tables of ASTM D1250-04 / API MPMS Chapter 11.1-2004 — the same methodology used for custody transfer worldwide. Tables 6/24/54/60 return the VCF directly; tables 5/23/53/59 return the base density or gravity.

How VCF is calculated

Supported product types

Each product type maps to the ASTM D1250-04 product group, which determines the table family and the applicable density ranges. The °API ranges shown below are the standard's commodity classification ranges; the exact input limits accepted per table are listed in the reference tables section below.

Reference tables

Tables 5–24 use temperatures in °F; tables 53–60 use °C. The API takes the table identifier and the temperature in the table's native unit — °F for 5/6/23/24, °C for 53/54/59/60. Temperatures outside −58 to 302 °F (−50 to 150 °C) are rejected, as are densities outside each table's published range.

Group C tables apply to special applications with an experimentally derived thermal expansion coefficient (α60, α15, or α20) and are available through the API.

API request

A single request returns the result for the requested table — the VCF for tables 6/24/54/60, or the base density/gravity for tables 5/23/53/59. One credit is deducted per successful calculation.

If the input values fall outside the valid range for the requested table, the API returns422with an invalid_input error. Out-of-range requests are not charged — no credit is deducted.

{
  "table": "6A",
  "temp": 86,
  "density": 35
}

{
  "request_id": "…",
  "table": "6A",
  "result": 0.98765,
  "credits_used": 1,
  "remaining_credits": 12,
  "metered_via": "credits",
  "remaining_quota": null
}

Glossary

API gravity

A density scale where lower API values mean denser liquid. Calculated from specific gravity: the higher the API gravity, the lighter the product.

VCF

Volume Correction Factor — the multiplier that converts a volume measured at observed conditions to the equivalent volume at standard (base) conditions.

Observed conditions

The temperature at which the liquid density or volume was measured. VCFAPI corrects for temperature only (API MPMS Chapter 11.1-2004); pressure correction (Chapter 11.2) is not applied.

Standard / base conditions

The reference temperature to which volumes are corrected for custody transfer — typically 60 °F, 15 °C, or 20 °C depending on the table family.

Relative density

The ratio of the density of the liquid to the density of water at a reference temperature (60 °F).

Standard volume

The corrected volume at base conditions, computed as observed volume × VCF. This is the value used for transactions and inventory.

Thermal expansion coefficient (α)

A measured property of a specific liquid (α60, α15, or α20) used by Group C tables instead of a density input. VCFAPI accepts the coefficient directly in the density field for tables 6C/24C/54C/60C.