API Gravity Calculator
Convert between API gravity and specific gravity / density for crude and products.
Higher API = lighter oil. Water is 10 °API; WTI ~39; Brent ~38; bitumen < 10 (sinks in water).
Formula
API Gravity Calculator is a free api gravity for process, mechanical and water engineers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About API Gravity Calculator
Convert between API gravity and specific gravity / density for crude and products. The calculation implements SG = 141.5 / (131.5 + °API) (ASTM D287 — API gravity of crude petroleum). Higher API = lighter oil. Water is 10 °API; WTI ~39; Brent ~38; bitumen < 10 (sinks in water).
How to use API Gravity Calculator
- 1Enter API gravity in °API.
- 2Read Specific gravity (60/60 °F), Density instantly — no submit button needed.
- 3Need US units? Flip the SI/Imperial toggle and every field converts.
Why use API Gravity Calculator?
- ✓Implements the standard formula — SG = 141.5 / (131.5 + °API)
- ✓Reference cited on-page: ASTM D287 — API gravity of crude petroleum
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Built-in engineering verdict flags out-of-range results instantly
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the API Gravity Calculator use?+
It computes SG = 141.5 / (131.5 + °API), per ASTM D287 — API gravity of crude petroleum. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
Higher API = lighter oil. Water is 10 °API; WTI ~39; Brent ~38; bitumen < 10 (sinks in water).
Does this work for any fluid?+
Yes — density and viscosity are inputs (with common fluids suggested in the field hints), so the same physics applies to water, oils, gases and process fluids. Compute always runs in SI internally, so unit mix-ups can't corrupt the result.
Is the API Gravity Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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