How much ink does a pen have in it?

The amount of ink in a pen can vary depending on the type of pen and its size. Here are some examples:

- Ballpoint pens: Ballpoint pens contain a thick, oil-based ink that flows through a small ball at the tip of the pen. The average ballpoint pen holds about 0.7 to 1.0 milliliters (mL) of ink.

- Gel pens: Gel pens contain a water-based ink that is thicker than ballpoint pen ink. The average gel pen holds about 0.5 to 1.0 mL of ink.

- Fountain pens: Fountain pens use a liquid ink that flows from a reservoir to the tip of the pen. The average fountain pen holds about 1.0 to 2.0 mL of ink.

- Rollerball pens: Rollerball pens use a water-based ink that is similar to fountain pen ink, but it is thicker and flows more easily. The average rollerball pen holds about 0.5 to 1.0 mL of ink.

It's worth noting that the capacity of a pen's ink reservoir can also vary depending on the brand and model of the pen.