Also available in Polish: README
A small set of round numbers that cover the whole range of everyday measurements — and fit together so you can scale anything without recalculating.
Instead of "a bit more", you use the next value up. Instead of multiplying by 1.6, you shift every value by the same number of steps. The numbers are designed to be memorable, and the steps are designed to be meaningful.
HSN works wherever you measure, experiment, or scale: cooking, training, finances, time, 3D modelling, game design, and more.
| Step | Value |
|---|---|
| 0 | 1 |
| 1 | 1.25 |
| 2 | 1.6 |
| 3 | 2 |
| 4 | 2.5 |
| 5 | 3.2 |
| 6 | 4 |
| 7 | 5 |
| 8 | 6.4 |
| 9 | 8 |
| 10 | 10 |
Then continues: 12.5, 16, 20, 25, 32, 40, 50, 64, 80, 100 …
The sequence is easy to memorize once you notice it consists of three simple series woven together, each doubling at every step:
- 1 — 2 — 4 — 8 (×2 each time)
- 1.25 — 2.5 — 5 — 10 (×2 each time)
- 1.6 — 3.2 — 6.4 (×2 each time, also recognizable as 16 — 32 — 64)
Common multiplications become simple step shifts:
| Operation | Steps |
|---|---|
| ×2 (or ÷2) | +3 (or −3) |
| ×3 (or ÷3) | +5 (or −5) — approximate |
| ×10 (or ÷10) | +10 (or −10) |
To double any quantity, shift 3 steps up. To scale down by a third, shift 5 steps down.
- Cooking — scale a recipe for one person or a whole family
- Training — progress from 3.2 to 4 to 5 km
- Finances — set pocket money that grows meaningfully with age
- Time — choose brewing or cooking durations from the time variant
- 3D modelling — pick dimensions that relate to each other consistently
- Game design — build a numeric scale for mechanics (e.g. a power meter)
For time, the sequence is adapted to hours and minutes:
| Step | Value |
|---|---|
| 0 | 1:00 |
| 1 | 1:15 |
| 2 | 1:36 |
| 3 | 2:00 |
| 4 | 2:30 |
| 5 | 3:12 |
| 6 | 4:00 |
| 7 | 5:00 |
| 8 | 6:24 |
| 9 | 8:00 |
| 10 | 10:00 |
| 11 | 12:30 |
| 12 | 16:00 |
| 13 | 20:00 |
| 14 | 25:00 |
| 15 | 32:00 |
| 16 | 40:00 |
| 17 | 50:00 |
| 18 | 1:00:00 |
Then continues in hours, with 1 day replacing the "25 h" step.
The time variant follows the same pattern — three series woven together, each doubling at every step:
- 1:00 — 2:00 — 4:00 — 8:00 (×2 each time)
- 1:15 — 2:30 — 5:00 — 10:00 (×2 each time)
- 1:36 — 3:12 — 6:24 (×2 each time, i.e. 1:30+0:06, 3:00+0:12, 6:00+0:24)
The recipe was developed by trial and error using HSN values, then scaled up by 2 steps (≈ ×1.6) to serve a larger family — without recalculating any proportions:
| Ingredient | Amount |
|---|---|
| Eggs | 3 |
| Milk | 500 ml |
| Wheat flour | 400 g |
| Baking powder | 1.6 tsp |
| Rapeseed oil | 100 ml |
Milk (500 ml) and flour (400 g) sit precisely on HSN values. Eggs come in whole numbers — rounded to the nearest integer. Baking powder at 1.6 tsp is an HSN value; in practice 1.5 tsp works equally well — a reminder that HSN is a starting point, not a constraint.
See also: Kitchen measuring tools specification
HSN is a human-oriented adaptation of the R10 Renard series (ISO 3, 1952) and is structurally similar to the E12 series used in electronics. Those systems were designed for manufacturing tolerances and inventory standardization. HSN is optimized for everyday human use: values are rounded to be memorable rather than mathematically exact, and the time variant has no equivalent in the Renard or E series.
The underlying step is 2^(1/3) ≈ 10^(1/10) — roughly 26% between adjacent values. The 1/3-stop ISO film speed sequence (…25, 32, 40, 50, 64, 80, 100…) uses the same step and is a well-known domain-specific instance of the same idea.
The only place where doubling does not work exactly is 6.4 × 2 = 12.8, rounded to 12.5 in HSN. This is a consequence of the near-coincidence 2^10 ≈ 10^3 (1024 ≈ 1000): the binary and decimal systems almost align after 10 steps, which is precisely what makes the sequence work so well across both. The rounding error at this single point is about 2.4%.
This is visible in the every-3-steps subsequence (each value ×2):
| 1 | 2 | 4 | 8 | 16 | 32 | 64 | 125 | 250 | 500 | 1000 |
The sequence follows powers of 2 exactly up to 64, then quietly switches to the decimal world at 125 — the point where 2^10 ≈ 10^3.
CC0 — public domain. No attribution required, though appreciated.