How to Learn the SI Units
Physics and chemistry run on the SI system — seven base units plus a ladder of prefixes from tera down to nano. Get these solid and unit conversions stop being scary. This deck covers both the base units and the prefixes.
There are 14 cards in the deck below. You can read through them, practise them right here with the flip-card player, and then save the deck to study properly with spaced repetition — the method that makes them stick for months, not minutes.
Why the SI base units and metric prefixes is hard to memorize (and the fix)
People mix up the base units (is the unit of current the amp or the volt?) and the prefix powers (is milli 10⁻³ or 10⁻⁶?). Both are pure memorization — perfect for flashcards.
The fix is active recall plus spaced repetition. Instead of re-reading the list (which feels productive but barely works), you test yourself — pull each answer out of memory — and you review each card on a schedule that stretches over time. Every time you successfully recall a fact, the memory gets stronger and the next review is pushed further out. That's how you go from "I saw it once" to "I just know it."
The fastest way to learn the SI base units and metric prefixes
- Break it into small batches. Split into two decks in your head: the 7 base units, then the prefixes. Learn the prefixes as a ladder in powers of ten.
- Test, don't re-read. Look at the question, say the answer out loud before flipping the card. The little struggle to recall is what builds the memory — a smooth re-read does almost nothing.
- Review on a schedule. Spaced repetition shows you each card right before you'd forget it. Get one right and it comes back in a few days, then a week, then a month. Miss one and it comes back sooner.
- Keep sessions short and daily. Five to ten minutes a day beats a two-hour cram every time. Consistency is the whole game.
One fact per card. Learn the symbol too (k, M, m, µ) — questions use the abbreviation.
The full deck: the SI Units
Here's every card in the set. Practise them above, or save the deck and let spaced repetition schedule your reviews automatically.
| Quantity / prefix | Unit / value |
|---|---|
| SI base unit of length? | Metre (m) |
| SI base unit of mass? | Kilogram (kg) |
| SI base unit of time? | Second (s) |
| SI base unit of electric current? | Ampere (A) |
| SI base unit of temperature? | Kelvin (K) |
| SI base unit of amount of substance? | Mole (mol) |
| SI base unit of luminous intensity? | Candela (cd) |
| What does the prefix "kilo" mean? | ×1,000 (10³) |
| What does the prefix "mega" mean? | ×1,000,000 (10⁶) |
| What does the prefix "giga" mean? | ×10⁹ (a billion) |
| What does the prefix "milli" mean? | ÷1,000 (10⁻³) |
| What does the prefix "micro" mean? | ÷1,000,000 (10⁻⁶) |
| What does the prefix "nano" mean? | 10⁻⁹ |
| What does the prefix "centi" mean? | ÷100 (10⁻²) |
Save this deck and actually remember it
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Study this deck free →FAQ: learning the SI base units and metric prefixes
How long does it take to learn the SI base units and metric prefixes?
Most people can lock in the SI base units and metric prefixes within one to three weeks of short daily sessions. With spaced repetition doing 10–14 cards a day, you'll recognise them within days and recall them reliably within a couple of weeks.
What's the best way to memorize the SI base units and metric prefixes?
Active recall plus spaced repetition. Test yourself instead of re-reading, and review on a schedule that spaces the cards out over time. Flashcards are built for exactly this — which is why the deck above is the fastest path.
Is this deck free?
Yes. You can practise all 14 cards on this page for free with no account. Sign up (also free) to save the deck and let spaced repetition schedule your reviews so it sticks long-term.