Decimal Format - AMA Manual of Style

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Decimal Format 

Units of Measure

Phil B. Fontanarosa

and Stacy Christiansen

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PRINTED FROM AMA MANUAL OF STYLE ONLINE ( © American Medical Association, 2009. All Rights Reserved. Under the terms of the license agreement, an individual user may print out a PDF of a single chapter of a title in AMA Manual of Style Online for personal use (for details see Privacy Policy).  Subscriber: null; date: 10 February 2016

Decimal Format

The decimal format is recommended for numbers used with units of measure. Numerical values less than 1 require placement of 0 before the decimal marker.





However, certain statistical values, such as α levels and P values, should be reported without the use of 0 before the decimal marker. (See 19.7.1, Numbers and Percentages, Forms of Numbers, Decimals; and 20.9, Study Design and Statistics, Glossary of Statistical Terms.)

The sample size was based on detecting a 10% difference in the primary outcome measure, using a 2-sided α level of .05.

Statistical significance was defined as P < .01.

Fractions should not be used with SI units.


2.5 kg


2½ kg

Mixed fractions occasionally are used in text to indicate less precise measurements and most commonly involve units of measure representing time.

After more than 7½ years of investigation, the effort to develop a new vaccine was abandoned.

The decimal format also could be used:

After more than 7.5 years of investigation, the effort to develop a new vaccine was abandoned.

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