📏 Length Steps
These are the ones worth knowing by heart. Each step is 10, 100 or 1000 — that's what makes metric easy.
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⏱️ Time Steps
Time is the odd one out — the steps are 60, 24, 7 and 365 instead of neat tens. There's no shortcut here, you just learn them!
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A normal year is 365 days, but every 4th year is a leap year with 366 — that extra day is February 29th.
The 7 Base Units
Every other unit in the SI system — like speed, area, or force — is built by combining these seven.
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Metric Prefixes
A prefix in front of a unit means "multiply or divide by 10 some number of times" — that's why 1 kilometer is 1000 meters.
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🔁 Convert Units
Pick a category
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Cool SI Facts
📏 The Meter's Wild History
The meter was first defined as one ten-millionth of the distance from the North Pole to the equator — today it's defined using the speed of light instead, which is much easier to measure precisely.
⚖️ The Kilogram Used to Be a Rock
Until 2019, "1 kilogram" officially meant the exact weight of one specific metal cylinder kept locked in a vault in France, nicknamed "Le Grand K". Now it's defined using a constant of nature instead.
⏱️ Time Doesn't Follow the 10s Rule
Most SI units use neat powers of ten, but time is the exception — there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day, a system left over from ancient Babylon.
🌡️ Kelvin Starts at Absolute Zero
0 Kelvin is the coldest anything can ever possibly be — about −273°C — the point where atoms have almost no energy left to move at all.
🎯 Unit Quiz
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