Weight is one of the most important components not only in science but also in daily life non-science routines. Weight can be defined as the force exerted on a body due to gravity. The weight W of a body is equal to the magnitude F of the gravitational force on the body. Businesses in the non-science world deal with product mass. The weight calculations in non-science entities are usually in the sales of the product for pricing per weight unit, translating it into costs and currency. In particular, weight and its conversion are of utmost importance among health care providers for managing patient care. 

Weight conversion is also utilized daily in health care. There are two systems calculating weight used in all healthcare settings for health management, such as medication dosing per patient body weight. Another example is the weight tracking in congestive heart failure patients. First, the metric system is in common use in health care in the US. It is also the only system universally used in many countries on all continents of the globe. It has the advantage of a decimal system in increments or the power of tenths. Hence it is widely used for ease of calculations. The metric system was adopted in US medical and pharmaceutical practices in the late 1800s.[1] It is currently used only in science and health care in the US. Second, the US weight system customarily uses the ounce or pound. It derives from the British colonial era. This non-metric system is still being used nowadays among laypersons in the US for products sold to the public. However, the scales in the US are calibrated for both metric and non-metric systems. The majority of the products sold in the US also are labeled with both weight systems. 

The metric system is essential in all health care settings. Patients are weighed at each clinical encounter. Scales used in the US has double marking indicators: metric and non-metric markings. Metric weight values are used in medication calculation, radiation dosing, and weight compliance in equipment use, such as the maximum weight of a CAT-SCAN unit or a surgical table that may hold a person. On the other hand, non-healthcare/non-science people have minimal understanding of the metric weight system. The American people prefer to understand weight as in ounce or pound.[2] When babies are born, their weight is one of the most important things recorded; metric weight is recorded in the electronic health records by clinicians and hospitals, and the family records non-metric weight for newborn announcements. Nowadays, all medications are based on weight for dose calculations for all populations but very specifically in children and infants. Adults have their weight recorded mainly by their doctors at each physical patient-clinician encounter.  Commonly, most adults monitor their weight for weight management. Clinicians record it in the electronic health records in both kilograms and pounds. However, communication with patients is generally in pounds by health care providers for weight reduction education. In non-medical areas, such as in the identification of suspects by American law enforcement, the pound unit in body weight is used for approximation. Hence, the American public can understand the estimated size of weight in a person.

Education on weight and its conversion started in grade school. The most important teaching of weight conversion between a pound to a metric weight, either grams or kilograms, is crucial throughout one's education. Universally, weight the following shorthand units are used in writing. 

• Pound = lb.
• Ounce = oz.
• Kilogram = kg.
• Gram = gm.

In general, 2.2 pounds roughly converts to 1 kilogram, and a kilogram equals approximately 2.2 pounds. 

Commonly in healthcare and medical practices, the metric system is used for weighing mass. In the metric system, there are increments at the power of the tenth for calculations. This weight conversion is used daily among scientists and health care providers.

• 1 kilogram (kg) = 1000 grams (gm) = 1,000,000 milligrams (mg) = 1,000,000,000 micrograms (mcg)

Another weight unit used in medical communities includes grains. Here is another weight conversion commonly used in the pharmaceutical industry.

• 1 grain (gr) = 60mg

Among US laypeople, weight units of the pound and ounce are almost universal. Americans are very familiar with this conversion, especially for daily cooking and baking. Shopping for produce in the markets in the US also utilizes this conversion.

• 1 pound (lb) = 16 ounces (oz)

In science experimentation, there are specific mathematical processes and formulas necessary for density calculations utilizing fluid weight. Liquids can be useful for measuring as in fluid weight measurement terminology, not to be mistaken as a dry weight for concrete materials or substances.

Fluid weight is commonly measured using the metric system for density calculations. Every liquid has a characteristic density (D) that is cataloged by scientists into the Density Table of Metals and Elements. It is defined as the ratio of its mass (m) to its volume (v) or in mathematical terms of D = m/v.  Density is usually given in units of kilograms/meter. When measuring small quantities, it's more convenient to use grams and cubic centimeters in this conversion.

• 1 kg/m = 0.001 g/cm; 1 g/cm = 1,000 kg/m

Due to the usage of both the metric and non-metric systems, clinicians receive training to be fluent in the calculations of common weight conversions in the patient weight for monitoring purposes, specifically in newborns or congestive heart failure patients. Weight conversion is necessary for record-keeping, which is usually in the metric system and for educating patients using a non-metric system. These are some common conversion factors:

• 1 lb   =  16 oz      =   453gm   =   0.45 kg
• 1 oz  =  0.063 lb  =   28 gm    =   0.03 kg
• 1 kg  =  1000 mg =   2.2 lb     =   35 oz
• 1 gm =  0.04 oz   =   0.001kg

It is universally understood that the metric system is used mainly in science and health care. Medical providers utilize weight conversion daily in their practice. It is important the address weight management with patients in the US due to increased obesity in many Americans. Clinicians need to speak correct weight terms among clinicians versus laypeople.[3] Weight affects greatly the pharmacokinetic and pharmacodynamic properties of medications. Improper use of weight conversion may lead to patient harm. 

Healthcare providers are tasked with weight management of the US population. Clinicians seeing patients must review charts for weight as well as body mass index in every encounter for weight monitoring in patients. This is the golden opportunity to educate patients on lifestyle changes for weight reduction purposes.[4] Obesity has been classified as a chronic illness and is managed by clinicians to prevent hypertension, kidney diseases, and many others.[5][6] Children in America are particularly important in weight management and education to parents with good choices of foods and exercises.[7]