How Long Will Your Ink Refill Actually Last, at How Much You Actually Write?

“How long does a refill last” has no single answer, because it depends on three things that vary from person to person: how much ink your tip lays down per page, how large you write, and how many pages you actually fill in a day. Two people with an identical pen can empty it on completely different schedules. Here's how those three factors combine, with worked numbers for the refill formats you're most likely to be choosing between.

The three inputs that decide everything

Ink consumption per page starts with tip type: a fine fountain nib lays down noticeably less ink than a broad one, and a fully liquid rollerball is wetter than either. On top of that, handwriting size scales consumption up or down — someone with large, loopy handwriting uses meaningfully more ink per page than someone with small, tight handwriting, even with the identical pen and nib. And finally, daily volume — how many pages you actually write per day — converts a fixed ink budget into a real-world timeline. Change any one of the three and the answer changes with it, which is exactly why a single number on a refill's packaging ("approx. 1,500 words") is never quite the answer you actually want.

A fountain pen cartridge, worked out

Take a standard international cartridge holding about 0.75 mL of ink, paired with a Fine nib, at one page of writing a day and medium-sized handwriting. Our ink refill life calculator puts a Fine nib's typical consumption at roughly 0.06 mL per page, which works out to about 13 pages from that single cartridge, or about 13 days at one page a day — a fresh cartridge roughly every two weeks. Switch the same 0.75 mL cartridge to a Broad nib instead, still at one page a day, and consumption roughly doubles to about 0.12 mL per page, cutting the same cartridge down to about 6 pages and 6 days — a Broad nib burns through cartridges at more than twice the rate of a Fine one, using the same ink.

A converter and bottled ink, worked out

A typical converter holds around 1.0 mL, a bit more than a disposable cartridge. Fill one, write with a Medium nib at two pages a day with average handwriting, and the calculator returns about 0.08 mL used per page, roughly 13 pages per fill, and about 6.5 days before you need to draw up more from the bottle — call it a refill from the bottle a little less than once a week for a moderate two-page-a-day habit. Handwriting size moves that number more than people expect: keep everything else the same but switch to large handwriting, and consumption rises to about 0.1 mL per page, dropping the fill to roughly 10 pages and 5 days; switch to small, tight handwriting instead and consumption falls to about 0.06 mL per page, stretching the same fill to about 16 pages and 8 days. Handwriting size alone swings the same 1.0 mL fill by a few days in either direction, entirely separate from which nib is installed.

Gel and rollerball refills, worked out

Sealed refills follow the same math, just with different per-page consumption figures. A 0.9 mL gel-medium refill at three pages a day comes out to roughly 18 pages per fill and about 6 days before it needs replacing. Swap that same 0.9 mL capacity into a finer gel tip at the same three pages a day, and the finer tip's lower per-page consumption stretches it to roughly 30 pages and about 10 days — the tip width matters as much for a gel pen as it does for a fountain nib. A 0.7 mL rollerball refill at two pages a day lands around 8 pages and 4 days, the shortest lifespan of the group here, because a rollerball's free-flowing liquid ink is the wettest of the common tip types per page written.

A heavy-use comparison: a piston filler at five pages a day

Higher-capacity filling systems change the picture at heavier writing volumes. A piston-filled pen holding around 1.4 mL, written with a Medium nib at five pages a day, comes out to roughly 18 pages per fill but only about 3.6 days — despite holding almost 40% more ink than the 1.0 mL converter example above, the much higher daily volume burns through it faster in absolute days, even though it still writes more total pages before running dry. This is the practical case for a higher-capacity filling system: it doesn't change how much ink a page needs, but it means fewer total refill events over a year for someone who genuinely writes that much, which the calculator also reports directly as a refills-per-year figure.

Matching refill format to your actual habits

Put the numbers together and a pattern falls out. A light, occasional writer — well under a page a day — will rarely notice much difference between cartridge, converter, or sealed refill formats, since even the thirstiest tip sips slowly at that pace and any of them lasts weeks. A moderate daily writer, in the one-to-three-page range, starts to feel the difference between a Fine nib's frugal cartridge life and a Broad nib's faster turnover, and this is where choosing a finer tip meaningfully cuts down on how often you're swapping ink. A heavy daily writer, five pages or more, is the person for whom filling system capacity actually starts to matter as much as tip size — a piston filler or a large-capacity converter cuts the number of refill events per week even though it doesn't change the ink-per-page math at all. For more on how tip choice and paper interact with everyday pen habits generally, see fountain, gel, or rollerball: which pen is right for you.

Estimating your own pages per day without a stopwatch

The “pages per day” input is the one people most often guess wrong, usually low. A single side of a standard notebook page, filled edge to edge with ordinary handwriting, is roughly 200 to 300 words. A daily journal entry of a few paragraphs is well under a full page for most people — often closer to a quarter or a half. Someone taking dense notes for a two-hour lecture or meeting can fill three or four pages without noticing. The honest way to find your own number is to count actual filled pages over a real week and divide by seven, rather than guessing from how it feels in the moment — writing almost always feels like more or less than it measurably is.

When capacity, not tip, becomes the bottleneck

Everything above assumes a fairly ordinary fill size. Vacuum-filling pens and some larger piston fillers can hold noticeably more than a standard 1.0–1.4 mL converter or cartridge, in some cases upward of 2 mL in a single fill. For a genuinely heavy daily writer — several pages a day, every day — that extra capacity is the main lever left to pull once tip size is already chosen for the line you want, since it directly multiplies the pages-per-fill and days-per-fill figures the calculator returns without changing anything about how the ink lays down on the page.

Buying a spare before you're caught without one

Once you know roughly how many days a fill lasts, buying a spare stops being guesswork. A rule that works well in practice: reorder or refill once you're inside the last 20% of the days-per-fill figure — for a cartridge that lasts about 13 days, that means having a spare in hand by around day 10 or 11, well before the pen actually runs dry mid-page. This matters more for less common cartridge standards, which can take longer to restock, than for near-universal formats like standard international cartridges or Parker-style refills, which are easy to find on short notice.

Running more than one pen at once

Plenty of people ink two or three pens at a time rather than one, which changes what “how long does it last” even means. Splitting the same daily page count across two pens roughly halves the effective pages-per-day figure for each one, stretching each individual fill's calendar life even though total ink consumption across both pens stays the same. This is a reasonable way to keep more than one ink color or nib width in daily rotation without any single pen running dry faster just because it's sharing the workload — the total ink used per day is unchanged, it's just distributed.

Why the numbers are estimates, not guarantees

Every figure above assumes a fairly typical A5-ish page of continuous writing and an average ink wetness for its category; real consumption shifts with how much white space is on the page, how wet a specific ink formulation runs, and how absorbent the paper is. Treat the calculator's output as a planning estimate — good enough to decide whether to keep a spare cartridge in a bag or order a fresh bottle — rather than a guarantee to the exact day. The relative comparisons hold up more reliably than the absolute numbers: a Broad nib will reliably use meaningfully more ink than a Fine one, and large handwriting will reliably outpace small handwriting, even if your specific mileage varies by a page or two either way.