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Trades Unit Converter - Pressure, Flow, Temperature & More for Industrial Workers

Purpose-Built Unit Conversions for Plumbers, HVAC Techs, Instrument Techs, and Millwrights

Free unit converter designed specifically for trades and industrial workers. Convert pressure, flow, temperature, torque, length, area, volume, mass, water chemistry, and electrical units including niche conversions that generic converters miss: inches of water column to PSI, grains per gallon to ppm, SCFM to ACFM, Cv to Kv, mil to inches, Newton-meters to foot-pounds, and more. Grouped by trade discipline so you find what you need without scrolling past irrelevant conversions.

Pro Tip: The conversion that trips up the most people in the field is SCFM to ACFM. Standard cubic feet per minute (SCFM) is referenced to standard conditions (14.696 PSIA, 68 degrees F, 36% RH). Actual cubic feet per minute (ACFM) is the volume flow at your actual pressure, temperature, and humidity. A compressor rated at 100 SCFM at sea level delivers roughly 83 ACFM at 5,000 feet elevation because the air is thinner. If you are sizing pipe, duct, or equipment at altitude, you must convert to ACFM first. Otherwise your pipe velocity and pressure drop calculations will be wrong.

Calculate pipe pressure drop using converted flow values

Pipe Pressure Drop Calculator →

Convert torque values for bolt tightening

Bolt Torque Calculator →

Read the trades unit conversion reference guide

Trades Unit Conversion Guide →
Start Using This Tool See How It Works

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Trades Unit Converter
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How It Works

  1. Select Category

    Choose a conversion category: pressure, flow, temperature, torque, length, area, volume, mass, water chemistry, or electrical. Categories are organized by trade discipline so HVAC, plumbing, instrumentation, and mechanical conversions are easy to find.

  2. Enter Value and Source Unit

    Type the value you want to convert and select the source unit. For example, enter 28 and select inches of water column (inWC) to convert a pressure reading.

  3. Select Target Unit

    Choose the target unit. The converter shows all available target units for the selected category. For the 28 inWC example, you can convert to PSI, kPa, bar, mbar, mmHg, atm, or other pressure units.

  4. View Results

    The converted value displays instantly with full precision. The converter also shows the conversion factor and formula used, so you can verify the math manually or use the factor in a spreadsheet.

  5. Use Quick-Convert Mode

    For frequently used conversions like inWC-to-PSI or F-to-C, use the quick-convert cards that show results for common reference values without selecting units each time.

Built For

  • Instrument technicians converting pressure readings between inWC, PSI, kPa, bar, and mmHg during calibration
  • HVAC technicians converting between SCFM and ACFM for air system sizing at altitude
  • Plumbers converting between GPM and liters per minute, or grains per gallon to ppm for water hardness
  • Millwrights converting torque between Newton-meters, foot-pounds, and inch-pounds during equipment assembly
  • Electricians converting between mil and inches for wire sizing, or between MCM and mm2 for conductor cross-section
  • Water treatment operators converting between mg/L, ppm, grains/gallon, and meq/L for chemical dosing
  • Mechanical engineers converting valve Cv to Kv for metric equipment specifications

Features & Capabilities

Pressure Conversions

Convert between PSI, inWC (inches of water column), kPa, bar, mbar, mmHg (torr), atm, inHg, Pa, and kg/cm2. Includes the critical inWC-to-PSI conversion (1 PSI = 27.68 inWC) used constantly in HVAC and instrumentation work.

Flow Conversions

Convert between GPM, LPM, m3/hr, CFM, SCFM, ACFM, and ft3/hr. The SCFM/ACFM conversion accounts for altitude, temperature, and pressure differences from standard conditions. Enter your actual conditions for accurate air flow conversion.

Temperature Conversions

Convert between Fahrenheit, Celsius, Kelvin, and Rankine with the correct offset formulas. Shows the formula alongside the result so you can verify. Includes common reference points: water freezing, boiling, body temperature.

Torque Conversions

Convert between foot-pounds (ft-lbs), Newton-meters (Nm), inch-pounds (in-lbs), and kilogram-meters (kgm). Essential for bolt torque specifications, which arrive in different units depending on whether the manufacturer is domestic or metric.

Water Chemistry

Convert between ppm, mg/L, grains per gallon, meq/L, and percent concentration. The grains-per-gallon to ppm conversion (1 GPG = 17.1 ppm) is used daily in water treatment and softener sizing. Also includes alkalinity, hardness, and conductivity unit conversions.

Valve Cv/Kv Conversion

Convert between Cv (US flow coefficient) and Kv (metric flow coefficient). Cv = 1.156 times Kv. Needed when specifying or comparing valves between US and European manufacturers. An often-overlooked conversion that causes sizing errors when mixed up.

Frequently Asked Questions

Both are pressure units, but inWC (inches of water column) is used for low pressures and PSI (pounds per square inch) for higher pressures. 1 PSI equals 27.68 inWC. HVAC ductwork static pressure is measured in inWC (typically 0.1 to 2.0 inWC). Gas piping supply pressure is measured in inWC (7 or 11 inWC). Pneumatic systems operate in PSI (80-125 PSI). Using the wrong unit is a common field mistake. If someone says the static pressure is 2.0 and does not specify units, ask whether they mean inWC or PSI because those are drastically different pressures.
ACFM = SCFM times (P_std / P_actual) times (T_actual / T_std), where pressures are absolute (PSIA) and temperatures are absolute (Rankine). Standard conditions are 14.696 PSIA and 528 degrees R (68 degrees F). At 5,000 feet elevation (12.23 PSIA) and 90 degrees F (550 degrees R): ACFM = 100 times (14.696/12.23) times (550/528) = 125.1 ACFM. The same mass flow rate occupies more volume at lower pressure and higher temperature. This matters for duct and pipe sizing because velocity depends on actual volume, not standard volume.
Cv (US flow coefficient) and Kv (metric flow coefficient) both describe valve flow capacity, but use different units. Cv is defined as the flow in US gallons per minute of water at 60 degrees F with a 1 PSI pressure drop. Kv is defined as the flow in cubic meters per hour of water at 16 degrees C with a 1 bar pressure drop. The conversion is Cv = 1.156 times Kv, or Kv = 0.865 times Cv. When comparing a Fisher valve spec (Cv) to a Samson valve spec (Kv), always convert to the same unit before selecting a size.
Multiply grains per gallon (GPG) by 17.1 to get ppm (or mg/L, which is essentially the same in dilute water solutions). For example, 10 GPG times 17.1 = 171 ppm. Water with less than 60 ppm is considered soft, 60-120 ppm moderately hard, 120-180 ppm hard, and above 180 ppm very hard. Water softener sizing, boiler blowdown calculations, and cooling tower chemistry all use these conversions routinely.
Google handles common conversions well but misses niche trades conversions. Try asking Google for inWC to PSI and it works. But try SCFM to ACFM at 5,000 feet and 90 degrees, or grains per gallon to meq/L, or Cv to Kv, and you are on your own. This converter groups conversions by trade discipline, includes the formulas, and handles the multi-variable conversions (like SCFM to ACFM) that require entering actual conditions. It is built for people who do these conversions daily, not occasionally.
Disclaimer: This converter provides unit conversion results for reference purposes. Always verify critical conversions with authoritative sources or engineering references. Conversion accuracy depends on the precision of input values and the applicability of standard conditions to your specific situation. ToolGrit is not responsible for errors resulting from unit conversion.

Learn More

Industrial

Trades Unit Conversion Reference: Pressure, Flow, Temperature, and Niche Conversions

Reference guide for trades-specific unit conversions including inWC to PSI, SCFM to ACFM, grains per gallon to ppm, Cv to Kv, and other conversions that generic tools miss.

Read Guide →

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