Nib Size & Dry Time Reference
Every round nib size in both Western and Japanese sizing, side by side with its line width, its equivalent size in the other standard, and how long it takes to dry on four common paper types — all computed from the same functions behind the Nib Size Converter and the Ink Dry-Time Estimator.
Western sizing
| Western (Pelikan, Lamy, Montblanc convention) | |||||||
|---|---|---|---|---|---|---|---|
| Size | Width | Cross-standard equivalent | Absorbent (cheap copy paper) | Standard (notebook / copy paper) | Coated (Rhodia, Clairefontaine) | Premium coated (Tomoe River) | |
| Extra Fine (EF) | 0.4 mm | Japanese F (0.35 mm) | 2s | 4s | 6.4s | 8.8s | |
| Fine (F) | 0.5 mm | Japanese M (0.5 mm) | 2.8s | 5.6s | 9s | 12.3s | |
| Medium (M) | 0.7 mm | Japanese B (0.7 mm) | 4s | 8s | 12.8s | 17.6s | |
| Broad (B) | 0.9 mm | Japanese BB (0.9 mm) | 6s | 12s | 19.2s | 26.4s | |
| Double Broad (BB) | 1.1 mm | Japanese BB (0.9 mm) | 8s | 16s | 25.6s | 35.2s | |
Japanese sizing
| Japanese (Pilot, Sailor, Platinum convention) | |||||||
|---|---|---|---|---|---|---|---|
| Size | Width | Cross-standard equivalent | Absorbent (cheap copy paper) | Standard (notebook / copy paper) | Coated (Rhodia, Clairefontaine) | Premium coated (Tomoe River) | |
| Extra Fine (EF) | 0.28 mm | Western EF (0.4 mm) | 2s | 4s | 6.4s | 8.8s | |
| Fine (F) | 0.35 mm | Western EF (0.4 mm) | 2.8s | 5.6s | 9s | 12.3s | |
| Medium (M) | 0.5 mm | Western F (0.5 mm) | 4s | 8s | 12.8s | 17.6s | |
| Broad (B) | 0.7 mm | Western M (0.7 mm) | 6s | 12s | 19.2s | 26.4s | |
| Double Broad (BB) | 0.9 mm | Western B (0.9 mm) | 8s | 16s | 25.6s | 35.2s | |
Dry times are computed at 50% relative humidity. Real humidity shifts every figure up or down together — see the FAQ below — without changing the relative ranking between sizes or paper types.
How this table is derived
Nothing in this table is a hand-typed number. Each row's width comes from calling widthFor(), the same lookup the Nib Size Converter uses; each cross-standard equivalent comes from calling convertStandard(), which matches a size to its closest counterpart by actual line width rather than by name; and each dry-time figure comes from calling estimateDryTime(), the same function behind the Ink Dry-Time Estimator, using that row's nib width category against each of the four paper types at a fixed 50% humidity. If either calculator’s underlying tables ever change, this reference and its test change with them automatically — there is no separate table to fall out of sync.
The pattern worth noticing: within either standard, dry time roughly quadruples from the finest size (EF) to the broadest (BB) on the same paper, and within any single size, dry time roughly quadruples again from the fastest-drying paper (absorbent) to the slowest (premium coated). Both effects compound together, which is why a Double Broad nib on premium coated paper takes so much longer to dry than an Extra Fine nib on absorbent paper — the two factors aren’t just added, they’re multiplied.
Frequently Asked Questions
Why does a Japanese Medium show a Western Fine as its equivalent?
Every equivalent size in this table comes from the same convertStandard() function the Nib Size Converter uses: it looks up the source size's typical line width, then finds the size in the target standard whose typical width is closest. A Japanese Medium's typical width (0.5mm) is closest to a Western Fine (also 0.5mm), not a Western Medium (0.7mm), which is exactly why Japanese nibs are widely described as running about one size finer than Western ones.
Why do the dry-time columns rise so much faster than the width column?
Width and dry time aren't on the same scale. Width increases by roughly 0.15-0.2mm between adjacent sizes, but dry time is the product of a nib-wetness factor and a paper-absorbency factor multiplied together, so small increases in either compound rather than add. A Broad nib's dry time isn't just a bit more than an Extra Fine's — it's roughly three times as much on the same paper, purely from that multiplication.
Why is every dry-time figure here computed at 50% humidity?
50% is the dry-time estimator's baseline — humidity of exactly 50% has a neutral 1.0 multiplier, neither speeding nor slowing the result. Real humidity shifts every figure in this table up or down together (roughly 30% faster at low humidity, 40% slower at high humidity) without changing which nib or paper combination is fastest or slowest relative to the others, so a single baseline humidity keeps the table's comparisons meaningful.
Does this table cover stub, italic, or oblique nibs?
No — this table covers only the five standard round sizes (EF, F, M, B, BB) that both the Nib Size Converter and the Ink Dry-Time Estimator model directly. Shaped nibs vary their width within a single stroke by design, so a single millimetre figure doesn't describe them the way it describes a round nib.
Widths and dry times are practical guides, not lab-measured figures for any specific pen, ink, or paper. Treat both as a starting point for comparison rather than an exact prediction.
Use it with
- Nib Size Converter— convert a single size between Western and Japanese sizing without scanning the whole table.
- Ink Dry-Time Estimator— get a dry-time estimate for your own nib, paper, and humidity, rather than the fixed 50% baseline used here.
- A Japanese Medium nib isn’t a Western Medium — the guide version of the sizing half of this table, with worked conversions and what the width difference looks like on the page.
- How long fountain pen ink takes to dry — the guide version of the dry-time half of this table, including left-handed smudging and what actually helps.