Concept 4 of 9
The Kitchen Scale: Measuring Weight
Today's big idea
Metric weight jumps by 1,000, and pounds jump by 16, so pick the system first.
Metric uses 1 kg = 1,000 g; pounds use 1 lb = 16 oz. Two systems, two jumps.
How it works
👀 What's going on?
How heavy is your school bag, or a bag of rice at the shop? Weight gets measured in grams for light things and kilograms for heavy ones, and a single number connects the two.
💡 Here's the trick
Look at the two scales above. Most of the world weighs in grams and kilograms, where 1 kg = 1,000 g. Some countries still use pounds and ounces instead, where 1 lb = 16 ounces. Each system has its own jump: metric jumps by 10, 100 or 1,000, while pounds jump by 16. Pick the system the question uses, then multiply to reach the smaller unit or divide to reach the bigger one.
🪄 How to do it
- 1.Spot which system you are in on the scales above, metric or pounds.
- 2.Heading to the smaller unit, multiply by that system's number. Heading to the bigger unit, divide by it.
✍️ Try it
Write a 3.5 kg backpack in grams, write a 500 g book in kilograms, then write a 2 lb bag of flour in ounces.
The backpack gives 3.5 x 1,000 = 3,500 g. The book gives 500 divided by 1,000 = 0.5 kg. The flour uses the pound system, so 2 x 16 = 32 ounces. Each number changed by its own system's jump, 1,000 for metric and 16 for pounds.
⚠️ Watch out
You might be thinking 500 g must be heavier than 0.5 kg, because 500 is so much bigger than 0.5. They are the identical weight. The unit is doing the work, not the digits.
🌟 Why this matters
Shopping labels, luggage limits and recipes all switch between grams and kilograms. Some imported recipes and older cookbooks still call for pounds and ounces, so both systems turn up in real life.
Exam tip: Write the unit beside every number, and never jump straight between the two systems in a single step.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“A 1.2 kg melon — how many grams?”
- 1
Big or small unit?
kg → g goes bigger to smaller → multiply.
- 2
Find the multiplier
1 kg = 1,000 g.
- 3
Multiply
1.2 × 1,000 = 1,200
- 4
Converted ✓
1.2 kg = 1,200 g
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Add 1-oz weights to the right side until the scale BALANCES with 1 lb!
Add 16 more oz
Quick check
✅ VERIFICATION
A bag of rice weighs 2.4 kg. How many grams is that?
⚡ Finish the activity above first to answer.
Keep going!
Up next: The Fence Builder
Add up all the sides of any shape.