- 1 Metric units and metric units of measure
- 1.1 Abbreviating metric units of measure
- 1.2 Capitalizing metric units of measure
- 1.3 Using hyphens with metric unit expressions
- 1.4 Using periods with metric unit expressions
- 1.5 Metric units with exponential expressions
- 1.6 Metric units expressed in multiplication of values
- 1.7 Expressing concentrations in metric units
- 2 Conventional (non-metric) units of measure
See also: Basic rules for percents, proportions, ratios and ranges.
A proportion is a ratio that expresses a relationship between part or parts, and the whole.
When the following conditions have been met, use a virgule in place of the word per:
1. There is at least one metric unit of measure, and;
2. At least one element includes a specific numeric quantity.
The dosage was calculated at 5 mcg/kg of body weight.
Meets the critieria of at least one metric unit of measure and a specific quantity
Dosage is measured in micrograms per kilogram of body weight.
Does not meet the criteria of a specific quantity
When the phrase does not include a metric unit of measure, spell out the word per and do not use a virgule. However, if an expression meets the criteria above and included a nonmetric unit of measure, use the virgule as outlined above.
Respirations are 18 per minute.
She sees her therapist 3 times per week.
Neither of these include a metric measurement
She takes 200 mg of ibuprofen 3 times per day.
The metric measurements is not part of the per expression
The IV will run at 5 mcg/min until the order is changed.
The metric measurement is part of the per expression; the phrase meets the criteria outlined above for using a virgule
The word per is spelled out when a prepositional phrase intervenes between the two units of measure.
The patient was instructed to take 81 mg of aspirin per day.
Prepositional phrase - in italics - intervenes between the measurement and the per expression