All 29 SI Base & Derived Units flashcards. Free.
The whole deck, not a sample — SI Base & Derived Units is 29 cards, which is no longer than the 30 we give away on every deck, so there is nothing left to charge for. 13 pages, US Letter, black and white. Grades 9–12.
No account, no email, no card details.
13 pages, and the backs are already right
Every front sheet is followed by its own back sheet with the rows reversed. Print double-sided, flip on the long edge, and answer number 7 is behind question number 7. Print a deck you built yourself, flip on the short edge, and every answer lands on the wrong card — which nobody finds out until sixty cards have been cut apart.
- 29 cards — counted out of the file, not rounded up
- Eight cards a sheet, with cut guides
- US Letter PDF, black and white, photocopier-friendly
- Print a set per student, every class, every year
29 cards, because the SI has exactly seven base units and exactly 22 coherent derived units with special names. The BIPM's own words: together they 'form the core of the set of SI units', and all other SI units are combinations of these 29. The number is fixed by the SI, not chosen to fill a deck.
Every card here is cited to two independent sources
Two different organisations — not a standards body and a website reprinting it — and a script refuses the card if the two disagree, so the check runs on every card rather than on the ones somebody remembered to look at. A second specialist then re-verified this deck from sources of their own, without reading our citations first. A further 5,420 cards across 30 other decks were read end to end by a subject specialist instead, and we say which is which on every deck rather than averaging the two into one flattering word.
What 29 printed cards do that a screen does not
A phone deck is one card at a time. A printed deck is a pile you can split: the ones you know, the ones you nearly know, and the ones you keep missing. That third pile is the entire study session, and it is the thing a scrolling app hides from you.
- Print once, use all year. The licence covers a set per student, every class, every year.
- No device, no login, no data. Works in a cover lesson, on a bus, or at a kitchen table. Grades 9–12, filed under science.
- Change what you disagree with. Every card loads into the free maker on this site. Reword it, drop it, add your own, reprint.
Here are all 29 cards
Check them against your own textbook before you spend anything.
- The second (s)
- Time — fixed by the caesium-133 hyperfine frequency ΔνCs = 9 192 631 770 Hz
- The metre (m)
- Length — fixed by the speed of light c = 299 792 458 m/s (US spelling: meter)
- The kilogram (kg)
- Mass — fixed by the Planck constant h = 6.626 070 15×10⁻³⁴ J s, not by any metal prototype
- The ampere (A)
- Electric current — fixed by the elementary charge e = 1.602 176 634×10⁻¹⁹ C
- The kelvin (K)
- Thermodynamic temperature — fixed by the Boltzmann constant k = 1.380 649×10⁻²³ J/K
- The mole (mol)
- Amount of substance — exactly 6.022 140 76×10²³ elementary entities (the Avogadro number)
- The candela (cd)
- Luminous intensity — fixed by Kcd = 683 lm/W for radiation of frequency 540×10¹² Hz
- The radian (rad)
- Plane angle — expressed as 1. The angle whose arc equals the radius; m/m is misleading, per BIPM
- The steradian (sr)
- Solid angle — expressed as 1. A whole sphere subtends 4π sr; m²/m² is misleading, per BIPM
- The hertz (Hz)
- Frequency — s⁻¹. For periodic phenomena only; for radionuclides use the becquerel
- The newton (N)
- Force — kg m s⁻²
- The pascal (Pa)
- Pressure and stress — N/m² = kg m⁻¹ s⁻²
- The joule (J)
- Energy, work and heat — N m = kg m² s⁻²
- The watt (W)
- Power and radiant flux — J/s = kg m² s⁻³
- The coulomb (C)
- Electric charge — A s
- The volt (V)
- Electric potential difference — W/A = kg m² s⁻³ A⁻¹
- The farad (F)
- Capacitance — C/V = kg⁻¹ m⁻² s⁴ A²
- The ohm (Ω)
- Electric resistance — V/A = kg m² s⁻³ A⁻²
- The siemens (S)
- Electric conductance — A/V = kg⁻¹ m⁻² s³ A²
- The weber (Wb)
- Magnetic flux — V s = kg m² s⁻² A⁻¹
- The tesla (T)
- Magnetic flux density — Wb/m² = kg s⁻² A⁻¹
- The henry (H)
- Inductance — Wb/A = kg m² s⁻² A⁻²
- The degree Celsius (°C)
- Celsius temperature — the same size as the kelvin: t/°C = T/K − 273.15
- The lumen (lm)
- Luminous flux — cd sr
- The lux (lx)
- Illuminance — lm/m² = cd sr m⁻²
- The becquerel (Bq)
- Activity referred to a radionuclide — s⁻¹. For stochastic decay only, never for frequency
- The gray (Gy)
- Absorbed dose and kerma — J/kg = m² s⁻²
- The sievert (Sv)
- Dose equivalent — J/kg = m² s⁻². Same dimensions as the gray, different quantity
- The katal (kat)
- Catalytic activity — mol s⁻¹
Questions
- How do I print them double-sided?
- Double-sided, flip on the long edge. Every front sheet is followed by its own already-mirrored back sheet, so print them in the order they come and every answer lands on its own card.
- Can I edit the cards?
- Yes, and that is half the point. Once you own the deck, the "Buy & edit" button here opens all 29 cards in the free flash card maker on this site — reword a definition, delete the ones you do not teach, add your own, and print at anything from two to nine cards a page, rather than the fixed eight of the PDF.
- Can I print a set for every student?
- Yes. Personal and classroom licence: unlimited printing, every class you teach, every year you teach it. It does not cover reselling the file or passing it on to a colleague.
- What if I find a card that is wrong?
- Tell us and we fix it, and we publish what changed. We have withdrawn a whole deck from sale for being out of date rather than quietly patch it.
- Do I need an account?
- No. The file downloads straight away — no account, no email, no card details.