Fountain pen ink capacity calculator

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Estimate how long a fill lasts and how quickly you work through bottles based on your writing routine.

Typical converters are often around 0.5 to 0.9 mL; piston fillers may hold more.

Accounts for the ink that is technically still in the pen but not worth chasing before a refill.

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Time per fill

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Enter pen capacity, writing volume, and bottle size to estimate pages per fill and refill cadence.

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Example calculations

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Everyday note-taker

Standard converter and office-week usage

A normal converter can disappear faster than expected once you write a few pages on most workdays.

Result: A typical converter fill can run out in under a week of steady note-taking.

Heavy journaler

Large pen with broad nib and daily writing

Wet nibs and long journaling sessions burn through fills quickly even when the pen holds more ink than a converter.

Result: Heavy daily writing often means measuring refill cadence in days, not weeks.

Occasional pocket pen

Lighter usage and fewer writing days

Moderate page count and fewer writing days stretch a small fill much farther than most enthusiasts expect.

Result: Lighter, less frequent writing can make even a small pocket fill last multiple weeks.

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