Convert API gravity to density or density to API using kg/m³, lb/ft³, or g/cm³ units for petroleum fluids at a 60°F reference quickly.

60°F (15.56°C) reference. Measurements at another temperature need a separate petroleum correction.

Reference and display settings

Approximations change the answer; 1000 is not the standard 60°F water value.

Density From API Formula

The following formula uses the default water reference of 999.016 kg/m³ at 60°F. Reference and display settings retain 998.9 and 1000 kg/m³ as explicitly labeled approximations; choosing either changes the result.

D = 141.5 / (API + 131.5) × 999.016
  • Where D is the Density From API (kg/m^3)
  • API is the API 
API to Density Conversion Table (at 60°F)
API (°API) Density (kg/m³) Density (lb/ft³) Density (g/cm³)
81013.33963.2611.013
10999.01662.3670.999
12985.09261.4970.985
15964.92060.2380.965
18945.55759.0290.946
20933.07458.2500.933
22.3919.12157.3790.919
25903.26456.3890.903
28886.27455.3280.886
30875.29954.6430.875
31.1869.37754.2730.869
32864.59253.9750.865
35849.01453.0020.849
37838.93652.3730.839
40824.26151.4570.824
42814.75950.8640.815
45800.91149.9990.801
50778.84748.6220.779
55757.96747.3180.758
60738.17646.0830.738
* Rounded to 3 decimals. Formula used: ρ (kg/m³) = 141.5 / (API + 131.5) × 999.016 (at 60°F). Unit conversions: 1 lb/ft³ = 16.018463374 kg/m³; 1 g/cm³ = 1000 kg/m³.

How to Calculate Density From API?

The following example problems outline how to calculate Density From API.

Example Problem #1:

  1. First, determine the API.
    1. The API is given as 55.
  2. Finally, calculate the Density From API using the equation above: 

D = 141.5/(API+131.5) * 999.016

The values given above are inserted into the equation below:

D = 141.5/(55+131.5) * 999.016 = 757.967 (kg/m^3)

Example Problem #2: 

For this problem, the variables needed are provided below:

API = 65

This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer. 

D = 141.5/(API+131.5) * 999.016 = ?