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Metric Measurements

The metric system of measurement is used in almost all countries throughout the world.  The notable exception is the United States.

The U. S. Congress established the metric system as the “preferred system of weights and measures” as part of the Omnibus Trade and Competitiveness Act of 1988.  An Executive Order issued by President George Bush in l991 requires every federal agency to use metric measurements in grants, contracts and other business related activities after October 1, 1992, “unless it is not economically feasible or is likely to cause significant inefficiencies or loss of market to U. S. firms.”  

For the marketing of paper, the conversion of the customary units to the metric system may be accomplished by the application of formulas to move from inches to millimeters and pounds to grams.

Sizes

The size of paper in metric measure is stated in millimeters.  There are 25.4 millimeters in one inch. The procedure is to multiply the inches by 25.4, and round off to the nearest millimeter.  

For example: to convert the size of standard letter size from inches to millimeters 8 1/2" x 25.4  mm = 215.9 mm and 11" x 25.4 mm = 279.4 mm. The measurement therefore becomes 216 mm x 279 mm.

Basis weight

The basis weight of paper and paperboard is stated in grams per square meter (g/m² ).  

To convert from basis weight in pounds the following formula may be applied equally to basis ream weights of any dimension, e.g. 17" x 22", 25" x 38", 24" x 36".

Multiply the basis weight by 1406.13 and divide by the square inches in the base sheet.

For example:

To convert from 20 lb. 17" x 22"/500:
20 lbs. x 1406.13 ÿ 374 = 75 g/m²

^{To convert from 50 lb. 25" x 38"/500:
50 lbs. x 1406.13 ÿ} 950 = 74 g/m²

^{To convert from g/m2}  to pounds the procedure is reversed:

Multiply the g/m² by the square inches in the base sheet and divide by 1406.13.

Tables follow and show the grams per square meter values for the most common basis weights.

Total Weight

The total weight should either be expressed in kilograms or metric tons.  

To convert:

How to write metric units

• When rounding off metric units to the nearest whole unit use the procedure now used for the customary units.

When the decimal is less than 0.5, the first whole number to the left of the decimal point does not change.

When the decimal is 0.5 or more, the first whole number to the left of the decimal point is increased by 1.

• If a number is less than one, a zero should be written to the left of the decimal point, e.g. 0.25.

• If it is desired to separate digits in groups of three do not use a comma.  Use only a space.

• Periods  are not  used after symbols, e.g. mm for millimeters.

• Although an “s” added to the names of units to make them plural, symbols are the same for both singular and plural.

Metric units of measure and their symbols

^{Conversion of the U. S. customary weights and measures to metric measurements}

^{Conversion of metric measurements to U. S. customary weights and measures}

^{International Standards Organization’s paper sizes}

^{In reference to sheeted paper, many countries in the world use sizes set in the International Standards Organization’s document ISO 216.  The ISO sizes are a series of sizes designated “A”, “B” and “C”, having a length-to-width ratio of 1.414.}  

^{The “A” series is the one predominantly used.  It starts with the AO size which has an area equal to a square meter.  Each time the long side of the paper is cut in half the new size maintains the same 1.414 ratio.  When AO is cut in half, two sheets of size A1 are created.  The half cut of A1 provides the A2 size.  This procedure may be followed down to the A8 size.  The most common however is A4 which is equal to 210mm x 297mm (8 1/4" x 11 11/16").}

ISO-216 —  A SIZES

^{Some organizations and individuals in the United States and Canada have assumed that conversion to metric units involves a change to these ISO sizes.  However, 216mm x 279mm, (8 1/2" x 11") is just as metric as 210mm x 297mm (ISO A4 size).}

Basis weight and grams per square meter
for most common paper weights

Basic formula:  To convert from basis weight in pound to grams per square meter, multiply the basis weight by 1406.13 and divide by the square inches in the base sheet.  For example, to convert from 20 lb. 17" x 22"/500, multiply 20 lbs. by the constant 1406.13 and divide by 374 = 75 g/m².