How to Convert Metric to Imperial?

MeyerFire University | G401.04

By Franck Orset

RESOURCES

• One-Page Summary [PDF]
• Notes Page [PDF]

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TRANSCRIPT

How to Convert from Metric to Imperial? 

Many tools can be found on internet for rapid conversion of units from one system to the other. Google, for example, can quickly convert many common units. 

Some excel files are also available for a quick conversion. 

The MeyerFire site also has a free unit converter under Toolkit, then Unit Converter. 

For the most common units, used for fire protection, the conversions are calculated as follows. 

For fire pumps and water supplies:

Flow is generally expressed in cubic meter per hour or liter per minute. These need to be converted into gallons per minute. 

One cubic meter per hour is 4.4 gpm and one l/min is 0.264 gpm.  

If liters per second or kg per second is used, one l/s, or kg/s is 15.85 gpm. 

This means that a 2000 l/min flow is 528 gpm, and 341 m3/h is 1500 gpm. 

A 94.6 l/s flow is 1500 gpm. 

Pressure is expressed in bars. One bar is 14.5 psi. 

This means that 12 bars is 175 psi. 

You can also convert meter of water column into feet of water column. One mH2O is 3.28 ft H2O. And one bar is 33.44 ft H2O. 

Power for diesel engine drives is expressed in kilowatt. 1 KiloWatt is 1.34 horsepower. 

This means that 150 kW engine is 201 hp. 

Volume for the water tanks is generally expressed in cubic meter. One cubic meter is 264.2 gallons. And one liter is 0.26 gallon. 

This means that a 500 m3, or 500,000 liters tank is 132,100-gallons.

For sprinkler systems:

Temperature in degrees Celsius. To convert Celsius into Fahrenheit, a formula needs to be applied. If T is the temperature in Celsius, the temperature in Fahrenheit is 9/5 of T plus 32 ((T * 9/5)+32). 

For example, 0°C is 32°F and 100°C is 212°F. The scale for Celsius has been defined under the different state of water under normal pressure conditions, with 0 for the freezing point and 100 for the boiling point. 

K-factor in Liters per minute per square root of bars, as the K factor is defined by the formula Q = K √P. A K factor of 1 in the metric system, corresponds to a K factor of 0.07 in the Imperial system. 

For example, K80 is K5.6 is K80 and K115 is K8.0. 

Thread and pipe diameters in millimeters. 1 millimeter is inch is 0.039 inch. 

For example, a 13 mm thread is ½ in. and a 100 mm pipe is 4 in. 

Design density in liters per minute per square meter or millimeter per minute. One mm/min is 0.0245 gpm/sq ft. 

This means that 10.2 mm/min is 0.25 gpm/sq ft. 

Spacing and distances, generally in meters. One meter is 3.28 feet and 1.1 yard. 

This means, for example, that 15 m is 49 ft. 

Area of application in square meter. One square meter is 10.75 square feet. 

This means that 10 3 m2 is 107 sq ft or 300 m2 is 3,225 sq ft. 

Speed for the velocity of water inside the pipes, in meter per second. One meter per second is 3.28 ft per second. 

This means that 6 m/s is 19.7 ft/s 

For gas protection systems:

Volume, for the application of the system or room size, expressed in cubic meter. One cubic meter is 35.7 cubic feet. This means that 90 m3 is 3,214 cu ft. 

Weight, for the quantity of gas, expressed in kilogram. One kilogram is 2.22 pounds. This means that 100 kg is 222 lbs. 

For heat and energy:

Energy delivered by a fire, generally expressed in KiloJoule or KiloCalorie. 1 kJ is 0.95 BTU and one kCal is 3.97 BTU. 

This means that a 50,000 kJ fire is equivalent to 47,500 BTU and 12,500 kCal is 49,625 BTU. 

Power delivered by a fire, generally expressed in Joule per second, or Watt, which are 2 names for the same unit. One Watt is 3.41 BTU/h. 

For example, 3,000 Watts is 10,230 BTU/h. 

Heat flux, generally expressed in kilowatt per square meter. One kilowatt per square meter is 317.5 BTU per hour and per square foot. 

Note that a kilowatt spread over 1 m2 is approximately equal to the radiant heat flux outdoors on a sunny day.

For Franck Orset, I’m Jeff Kelm, this is MeyerFire University.