Metric & Imperial Conversion
Understand and use approximate equivalences between metric units and common imperial units (inches, pounds, pints)
What a learner can do afterwards
- State that 1 inch ≈ 2.5 cm and use this to estimate length in inches
- Know that 1 kg ≈ 2.2 pounds and estimate a person's weight in pounds
- Convert approximately between litres and pints (1 litre ≈ 1.75 pints)
The lesson
Some places measure in metric units, like centimeters, kilograms, and litres. Other places also use imperial units, like inches, pounds, and pints. Both measure the same real-world sizes, just with different numbers. You don't need to be exact. A close estimate is enough.
A baby weighs 7 pounds. To estimate kilograms, divide by about 2.2: 7 divided by 2.2 is close to 3.2. So a 7-pound baby weighs a little over 3 kg.
Quick trick: to turn kilograms into pounds, double the number, then add a bit more. To turn litres into pints, add three quarters of the number you started with.
Remember the three swaps: about 2.5 cm to an inch, about 2.2 pounds to a kilogram, and about 1.75 pints to a litre.
Watch it
Where it sits
Learn first
This opens up
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.