Imperial & Metric system

Weights and measures – Imperial and metric system

Weights: Weight is the measure of gravitational force acting on the body and weight is directly proportional to the mass of the body. The mass always remains constant. Weight varies with latitude, altitude, temperature, and pressure.

Measure: Measure the measurement of the volume of any substance. Measures of the liquids and gases vary with pressure and temperature.

There are two systems for the weights and measures. These are the Imperial system and the Metric system. The Metric system also known as the decimal system is based on related and rational units. Such as centilitre, millilitre, liter, gram, kilogram. Milligram, etc. The metric system is accurate and easy to calculate. Thus, THE metric system is widely used.

Imperial system: It is a system of measurement used in the United Kingdom and Commonwealth countries. The imperial system was also used in the USA but with slight variations. The imperial system is the oldest system of weights and measures. It is based on the unrelated units. It is not in use due to being less user-friendly than the metric system and not universally recognized. Some examples of units for weights are grains, ounces, ponds, etc. Some examples of units for volume are fluid ounce, quart, pint, gallon, etc.

There are two types of Imperial systems.

Apothecary system: It is also called the Troy weight system. It was related to the Roman system of measurement. It was based on unit grain (gr) to measure weight and fluid ounce (fl oz) to measure volume. However, other units used in the apothecary system were pint, minims, fluid dram, and fluid ounce. It is an old system, traditionally used by pharmacists to dispense medicines in the United Kingdom and Commonwealth countries.

Measurement of volume (capacity) comparison Imperial system: apothecaries British and U. S. System

Unit of Measurement: 1 Ounce   

• Imperial System (British):  1 Fluid ounce 

• Metric System:  28.41mL

•  U S System:    1 fluid ounce

• Metric System: 29.7 mL                           

Unit of Measurement: 1 Cup

• Imperial System (British):   Not in Use

• Metric System:                                         

• U S System: 8 Fluid Ounce         

• Metric System: 236.59 mL

Unit of Measurement:    1 Pint                     

• Imperial System (British): 20 fluid ounce                         

• Metric System: 568.26mL       

• U S System:16 fluid ounce         

• Metric System: 473.18 mL

Unit of Measurement:        1 quart                    

• Imperial System (British): 40 fluid ounce                         

• Metric System: 1.173 L           

• U S System: 32 fluid ounce 

• Metric System: 946.36 mL

Unit of Measurement:     1 gallon                      

• Imperial System (British): 160 fluid ounce                       

• Metric System: 4.546 L   

• U S System: 1128 fluid ounce

• Metric System:3.785 mL

Measurement of weights in apothecary

• 1 drachm = 60 grains

• 1 ounce = 8 drachm

• 1 ounce (oz)= 480 grain

• 1 pound (Lb)= 12 ounce

• 1 pound (Lb) = 5760 grain

  2. Avoirdupois system: It was primarily used in the USA and IN some other English-speaking countries. The avoirdupois system was used for the household items. Ounce was the unit for weight. Teaspoon (abbreviated tsp), tablespoon (abbreviated T), fluid ounce, cup (c), pint (pt), quart (qt), and gallon (gal) were used to measure volume.

Measurement of volume

•  1 gallon = 4 quarts = 8 pints =16 cups = 128 fl = oz 256 = tablespoonful (T) = 768 teaspoonful (tsp)

• 1 quart = 2 pints = 4 cups = 32 fl oz = 64 T = 192 tsp

• 1 pint = 2 cups =16 fl oz = 32 T = 96 tsp

• 1 cup =8 fl oz =16 T= 48 tsp

• 1 fl oz = 2 T = 6 tsp

• 1 T = 3 tsp

Measurement of Weight

• 1 Pound = 16 ounces

• 1 Pound = 7000 grain

• 1Ounce = 437.5 grain

Metric system: The metric system is also called the decimal system or the International system of units (SI). It has universal recognition. It consists of standardized units to measure physical quantities.

The metric system consists of seven base units. Among them, two are used as base units in pharmacy. These are liter and kilogram. The metric system uses prefixes to denote multiples of the base units. These prefixes are used for both very large and very small amounts. The metric system uses the same base units and prefixes for all types of measurements. The most commonly used prefixes in pharmacy are

• · Kilo (k) = 1.000 times of the base unit,

• Centi (c) = 1/100 (0.01) of the base unit

• Milli (m) = 1/ 1000 (0.001) of the base unit.

Measurement of Weight in Metric System

• 1 kilogram = 1000 grams

• 1 gram = 1000 milligram

• 1 milligram = 0.001 gram

• 1 gram = 1000,000 microgram

• 1milligram = 1000 micrograms

• 1 microgram = 0.000,0001 gram

• 1 microgram = 0.001 milligram.

Measurement of Capacity

• · 1litre = 1000 millilitre

Conversion metric system to Imperial system: Pharmacopoeia of India and all official pharmacopeia use the metric system. However, pharmacists must have the knowledge to convert the metric system to the imperial system and vice versa.

• Weight Measurement Conversion

  • 1Kilogram = 2.2 pounds (Lb)450 grams = 1 pound (avoirdupois system)

  • 30 grams = 1 ounce

  • 1 gram = 15 grains

  • 60 milligram = 1 grain

• Capacity Measurement Conversion

  • 1000 millilitre = 1 quart

  • 500 millilitre = 1 pint

  •  4 millilitre = 1 fluid drachm

  •  1 millilitre = 15 minims

  •  0.06 millilitre = 1 minim

• Domestic Measure Conversion

  • 1 drop = 1 minim = 0.06 milliliter

  • 1 teaspoonful = 1 fluid drachm = 4 millilitre

  • 1 dessertspoonful = 2 fluid drachm = 8 millilitre

  • 1 tablespoonful = 4 fluid drachm = 15 millilitre

  • 2 tablespoonful = 1 fluid ounce = 30 millilitre

  • 1 wine glass = 2 fluid ounce = 60 millilitre

  • 1 teacupful = 4 fluid ounce = 120 millilitre

  • 1 tumbler full = 8 fluid ounce = 240 milliliter

Author: Alok Bains