Convert the three quantities chemical and process engineers juggle most — volumetric flow, pressure, and dynamic viscosity — between SI and customary units. Pick a category, enter a value, and choose the from- and to-units to see the converted result and the equivalent SI base value.
Process data arrives in a jumble of units — flow in GPM or m³/h, pressure in psi, bar, or mmHg, viscosity in centipoise or poise. Plugging the wrong unit into a correlation is one of the most common and most expensive mistakes in process engineering. This converter handles the three quantities that cause the most trouble, always routing through the SI base unit so the conversion is exact and transparent.
Every unit is stored as a factor — the number of SI base units it represents. To convert, the tool multiplies your value by the from-unit factor to reach the base unit (m³/s for flow, Pa for pressure, Pa·s for viscosity), then divides by the to-unit factor: result = value × factor[from] / factor[to]. Going through a single base unit avoids the error-prone web of direct pairwise conversions and makes every result auditable.
Dimensional equations like Reynolds number, Darcy-Weisbach, and the ideal gas law only give correct answers when every quantity is in a consistent unit system. A friction-factor correlation fed viscosity in centipoise instead of Pa·s is wrong by a factor of 1000; a pressure-drop result in psi mistaken for bar is off by ~15×. Converting everything to SI before calculating, then converting back at the end, is the safest discipline.
Viscosity is almost always tabulated in centipoise (cP), and water at 20 °C is conveniently about 1 cP — but the SI unit is the pascal-second, with 1 cP = 0.001 Pa·s. Forgetting the factor of 1000 is endemic. Pressure has a second trap: gauge vs absolute. Gauge pressure is measured relative to atmosphere, so absolute = gauge + ~101.325 kPa. The ideal gas law and vapor-pressure work need absolute pressure; this converter handles only the unit scale, so add the atmospheric offset yourself when moving between gauge and absolute.
The SI base for volumetric flow is the cubic metre per second (m³/s), for pressure the pascal (Pa = N/m² = kg/(m·s²)), and for dynamic viscosity the pascal-second (Pa·s = kg/(m·s)). Customary units are defined exactly against these: 1 US gallon per minute = 6.30902×10⁻⁵ m³/s, 1 psi = 6894.76 Pa, 1 atm = 101325 Pa, 1 mmHg = 133.322 Pa, 1 poise = 0.1 Pa·s. Knowing the base unit makes every other conversion a single multiplication.
Multiply by 0.001: 1 cP = 0.001 Pa·s, so water at about 1 cP is 0.001 Pa·s. Equivalently, 1 Pa·s = 1000 cP. The intermediate unit poise (P) equals 0.1 Pa·s, so 1 P = 100 cP. Select the Dynamic viscosity category to do this exactly.
No — it converts between pressure units of the same kind (the scale only). Gauge and absolute differ by the atmospheric pressure offset, about 101.325 kPa or 14.696 psi. To get absolute pressure, add atmospheric to the gauge reading before or after converting units. The ideal gas law and Antoine vapor-pressure tools require absolute pressure.
The cubic metre per second (m³/s). Common practical units convert exactly to it: 1 m³/h = 1/3600 m³/s, 1 L/s = 0.001 m³/s, 1 US gallon per minute = 6.30902×10⁻⁵ m³/s, and 1 ft³/s = 0.0283168 m³/s. This tool uses m³/s as the base for all flow conversions.
Storing one factor per unit (its value in the SI base) and converting as value × factor[from] / factor[to] needs only N factors for N units, instead of N² pairwise conversions. It is less error-prone, easy to audit, and lets you add a new unit by defining a single factor. The displayed SI base value also serves as a check.
No. This converter uses the US gallon (1 US GPM = 6.30902×10⁻⁵ m³/s). The Imperial (UK) gallon is about 20% larger (1 Imp gallon ≈ 4.546 L vs 3.785 L for US). Always confirm which gallon a flow figure refers to, because mixing them introduces a ~20% error.