Overview
Read
Next Steps
Read
How to Measure Weight
This lesson explains how to measure weight using metric units like grams and kilograms and customary units like ounces and pounds. It covers the tools used to measure weight, how to read a scale, and how to convert between units of weight with simple, worked examples.
What Does It Mean to Measure Weight
To measure weight, we compare how heavy an object is against a standard unit. Small, light objects like a paperclip or a strawberry are measured in small units, while heavy objects like a bag of rice or a person are measured in larger units. Choosing an appropriate unit is closely related to estimating weight and capacity before you ever pick up a tool to measure.
Units of Weight
There are two common systems used to describe weight: the metric system and the customary (U.S.) system.
| System | Unit | Symbol | Example object |
|---|---|---|---|
| Metric | gram | g | a paperclip (about 1 g) |
| Metric | kilogram | kg | a textbook (about 1 kg) |
| Customary | ounce | oz | a slice of bread (about 1 oz) |
| Customary | pound | lb | a loaf of bread (about 1 lb) |
Grams and ounces are used for light objects, while kilograms and pounds are used for heavier ones. This is the same idea used when measuring capacity, where small units like milliliters and large units like liters serve different-sized amounts of liquid.
Tools Used to Measure Weight
Weight is measured with scales. Two common types are the balance scale and the spring or digital scale.
- Balance scale: compares the weight of an object to known weights placed on the other side until the two sides balance.
- Spring or digital scale: shows the weight directly on a dial or screen when an object is placed on it.
Reading a Scale
When reading a scale, look at the unit labeled on the dial or display, then read the number the pointer lands on, or the digital readout. Always double check whether the scale is showing grams, kilograms, ounces, or pounds, since mixing up units is one of the most common mistakes when measuring weight. Once you have two weights recorded, it becomes useful to line them up side by side, similar to how you would when comparing weight and capacity of different objects.
Converting Between Units of Weight
Because \(1\) kilogram equals \(1000\) grams, converting between the two is a matter of multiplying or dividing by \(1000\). If \(G\) stands for the number of grams and \(K\) stands for the number of kilograms, then:
\( K = \dfrac{G}{1000} \) and \( G = 1000K \)
For example, if an object weighs \(3500\) grams, then \(K = \dfrac{3500}{1000} = 3.5\), so the object weighs \(3.5\) kilograms.
Similarly, \(1\) pound is equal to \(16\) ounces, so to change pounds to ounces you multiply by \(16\), and to change ounces to pounds you divide by \(16\).
Worked Example
A bag of apples weighs \(2\) kilograms and \(250\) grams. What is the total weight in grams?
First, convert \(2\) kilograms to grams: \(2 \times 1000 = 2000\) grams. Then add the remaining grams: \(2000 + 250 = 2250\). The bag of apples weighs \(2250\) grams in total.
Why Measuring Weight Matters
Accurate weight measurement is used in cooking, shipping, health, and science. Choosing the right unit, using the right scale, and converting correctly all work together so that a measured weight actually means something useful in the real world.