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Engineering unit converter

Pick the quantity, type the value and see it converted to every unit used in engineering, from psi and inH₂O to bar and kgf/cm², with exact factors.

Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.

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The Metric/Imperial switch at the top only changes the table order and the highlighted unit; the value you type stays in the from unit.

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All units of the quantity

The report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. In the print dialog, choose Save as PDF.

Method, assumptions and references

Equations used

Base value = value × from-unit factor + offset; converted value = (base − offset) ÷ to-unit factor
Exact definitions: 1 in = 0.0254 m; 1 lb = 0.453 592 37 kg; 1 kgf = 9.806 65 N; 1 lbf = 4.448 221 615 260 5 N; 1 US gal = 3.785 411 784 L; 1 cal(IT) = 4.1868 J; 1 Btu(IT) = 1,055.055 852 62 J; 1 atm = 101,325 Pa
Temperature: K = °C + 273.15; K = (°F + 459.67) × 5/9; K = °R × 5/9
Derived: 1 hp = 550 ft·lbf/s = 745.699 87 W; 1 PS = 735.498 75 W; 1 ton of refrigeration = 12,000 Btu/h = 3,516.853 W; 1 inH₂O = 249.089 Pa; 1 inHg = 3,386.389 Pa

Assumptions and limits

  • Liquid columns at conventional values (water at 1,000 kg/m³, mercury at 13,595.1 kg/m³, g = 9.806 65 m/s²); for real readings, correct for fluid temperature.
  • Calories and Btu use the International Table (IT) definition. Normal and standard flows converted as ideal gas at the same reference pressure.
  • Results are shown to 7 significant digits; round to match the precision of the source value.

Standards and technical documents

  • NIST Special Publication 811 (2008): Guide for the Use of the International System of Units (SI), Appendix B
  • BIPM: The International System of Units (SI Brochure), 9th ed., 2019
  • NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, Appendix C
  • ISO 80000-1: Quantities and units — General
  • ISO 13443: Natural gas — Standard reference conditions

U.S. regulations

  • Metric Conversion Act of 1975 (15 U.S.C. 205a et seq.)
  • Fair Packaging and Labeling Act (15 U.S.C. 1451 et seq.): dual metric and US customary labeling
  • Executive Order 12770 (1991): metric usage in federal programs

Frequently asked questions

How many bar is 100 psi?

100 psi = 6.894 757 bar = 689.476 kPa = 7.031 kgf/cm². In a quick estimate, 1 bar ≈ 14.5 psi.

How do I convert hp to kW?

1 hp = 0.745 700 kW and 1 metric horsepower (PS or cv) = 0.735 499 kW. A 50 hp motor is 37.3 kW. European and Brazilian data sheets often list cv or PS, which is 1.4% smaller than hp.

What is the difference between scfm and cfm?

scfm is gas flow referred to standard conditions (60 °F and 14.696 psia here); cfm or acfm is volume at actual pressure and temperature. In the normal-flow category, 100 scfm = 160.7 Nm³/h at 0 °C.

How many Btu/h is one ton of refrigeration?

One ton of refrigeration is exactly 12,000 Btu/h, which equals 3.517 kW or 3,024 kcal/h.