Free Oilfield Unit Converter

This free oilfield unit converter is designed specifically for petroleum engineers, drilling engineers, reservoir engineers, and production engineers who need fast, reliable unit conversions on the job. Whether you are converting wellbore pressures from psi to bar, production volumes from barrels to cubic meters, or mud weight from ppg to specific gravity, this tool handles it instantly with no sign-up and no ads.

The converter supports 12 categories of units commonly used in oil and gas operations: pressure (psi, bar, kPa, MPa, atm, kg/cm²), volume (bbl, m³, gallons, liters, ft³, Mcf, MMcf), flow rate (bbl/d, m³/d, gal/min, L/s, Mcf/d, MMcf/d), length (ft, m, in, cm, miles, km), density and mud weight (ppg, SG, kg/m³, lb/ft³, psi/ft, kPa/m), API gravity (API to SG with the standard nonlinear formula SG = 141.5 / (API + 131.5)), temperature (°F, °C, K, °R), permeability (millidarcies, darcies, m²), viscosity (centipoise, Pa·s, lb/(ft·s)), energy (BOE, Mcf gas, MMBtu, GJ, kWh), force and torque (lbf, N, kN, ft-lbf, N·m), and area (acres, hectares, sq ft, sq m, sq miles, sq km).

All calculations run entirely in your browser. No data is sent to any server. Conversion factors are sourced from the Society of Petroleum Engineers (SPE) standards and NIST reference tables. Results update in real time as you type, so there is no need to click a button or wait for a response.

Built by Groundwork Analytics, an AI and engineering company that builds digital tools and deploys AI agents for the energy industry. We help operators, service companies, and engineering teams automate workflows, optimize operations, and make better decisions with their data. Get in touch or email us at info@petropt.com.

Petroleum engineering is one of the few disciplines that routinely mixes imperial, metric, and industry-specific units in the same calculation. This is not by choice — it is the result of over a century of operational history. The American oil industry standardized on feet, pounds per square inch, barrels, and pounds per gallon in the early 1900s through API (American Petroleum Institute) standards. Meanwhile, international operations adopted SI units (meters, pascals, cubic meters, kilograms per cubic meter). Today, most engineers work with both systems daily, and conversion errors remain a genuine source of costly mistakes.

Conversions Every Petroleum Engineer Must Know

• Volume: 1 barrel (bbl) = 0.158987 m³ = 42 US gallons. Barrels are the standard unit for oil volumes worldwide, while gas is measured in thousand cubic feet (Mcf) or million cubic feet (MMcf) in the US and cubic meters elsewhere.
• Pressure: 1 psi = 6.89476 kPa = 0.06895 bar. Psi dominates US drilling and production operations, while bar is common in European and Middle Eastern contexts. Knowing the quick approximation — 1 bar is roughly 14.5 psi — is useful for mental math.
• Density / Mud Weight: 1 ppg = 0.11983 SG (specific gravity relative to water). The conversion between ppg and pressure gradient is: psi/ft = ppg × 0.052. This factor appears in nearly every drilling calculation.
• API Gravity: API = (141.5 / SG) − 131.5. This nonlinear scale was designed so that most crude oils fall in a convenient 10–50 range. Light oil is above 31 API, medium is 22–31, and heavy oil is below 22.

Field Units vs. SI Units

Field units (also called oilfield units or customary units) include bbl, ft, psi, ppg, °F, md (millidarcies), and cp (centipoise). SI units use m³, m, Pa, kg/m³, °C, m², and Pa·s. Most reservoir simulation software accepts both systems, but mixing them in input files is a common source of simulation crashes and incorrect results. Always verify which unit system your software expects before entering data.

Common Unit Errors That Cause Real Problems

• ppg vs. SG in kill sheets: Confusing mud weight in ppg with specific gravity when calculating kill mud weight can result in a kill mud that is far too light or too heavy, directly impacting well control safety.
• bbl vs. m³ in reserves reporting: A factor-of-six error (1 m³ = 6.29 bbl) in reserves can misstate the value of an asset by hundreds of millions of dollars.
• Mcf vs. MMcf: Dropping or adding three zeros in gas volumes is surprisingly common in spreadsheets. One Mcf is 1,000 cubic feet; one MMcf is 1,000,000 cubic feet.
• Temperature offsets: Unlike most unit conversions, temperature requires an offset (not just a multiplier). Forgetting the 32°F offset when converting to Celsius is a classic error that affects PVT correlations and fluid property calculations.