About PenPeg
PenPeg is an independent, advertising-supported site for people who write with pens — fountain, gel, and rollerball — and care about the ink, paper, and nibs that go with them. It offers six free calculators and reference guides, a blog, and a Museum of Writing Instruments, and nothing here requires an account or a payment.
How the calculators are built
The Ink Cost Per Page Calculatordoes arithmetic you could do yourself, just faster: divide a cartridge’s price by the pages it writes, or a bottle’s price by its volume divided by how much ink one page uses. The default for that last figure is 0.005 mL per page, a reasonable estimate for a fine nib doing everyday note-taking — broad, wet, or flex nibs use several times more, so the tool lets you enter your own number instead.
The Ink Bottle Life Calculatorruns the same building blocks in reverse. It divides a bottle’s volume (typically 30-50 mL) by how much a converter or piston filler holds per fill (roughly 0.6-1.5 mL) to estimate refills, then works out how many pages and how many days or years that is at the writing pace you enter.
The Writing Time Calculatormultiplies a word count by a words-per-minute figure — about 13-20 wpm for handwriting and 40-70+ wpm for typing — and can run the sum backwards to show how many words you can fit into the time you have, using 250 words as a default page length.
All three run entirely in your browser: the numbers you type in are used to compute a result on the spot and aren’t sent anywhere.
Where the guides get their numbers
The Fountain Pen Nib Size Guidelists typical Western line widths in millimetres — about 0.3 mm for Extra Fine up to 1.1 mm for Double Broad — and notes that Japanese nibs from makers such as Pilot, Sailor, and Platinum tend to write about one size finer than their Western equivalents.
The Paper Weight & GSM Guideconverts between grams per square metre and US pounds using the standard factor for each paper grade — 3.7607 for bond/writing/copy paper, 1.4805 for text/book stock, and 2.7048 for cover/cardstock — which is why a 20 lb bond sheet and an 80 lb cover sheet are nowhere near the same actual weight.
The Pencil Grade Guidelays out the graphite hardness scale from 9H to 9B and maps the European HB letters to the US number system — a #2 pencil is exactly an HB.
What PenPeg is and isn’t
PenPeg is independent and isn’t affiliated with any pen, ink, or paper brand, or with the standards bodies behind gsm or pound-weight conventions. Every figure on the site is a general estimate built from common stationery conventions, not a guarantee — real-world results depend on the specific pen, ink, and paper you use, so treat the calculators as a starting point and verify before you buy. The site is supported by advertising, which is how it stays free. To go deeper on the history behind the tools, the Museum of Writing Instruments and the Learn section cover fountain pens, inks, and writing history in more depth, and the blog covers pens, ink, and paper more casually.
Spotted an error in a formula, or want a tool added? See Contact.