Ink Capacity in Pens: Ballpoint, Rollerball, Gel, and Fountain Pens Compared

Ink capacity varies by pen type, size, and design. Below are typical ranges for standard pens:

Typical Ink Volumes

Pen Type	Ink Type	Average Capacity
Ballpoint	Oil-based, viscous	0.7 – 1.0 mL
Rollerball	Water-based, thinner	0.5 – 1.0 mL
Gel	Water-based gel	0.5 – 1.0 mL
Fountain Pen	Liquid ink (cartridge/converter)	1.0 – 2.0 mL (cartridge); up to 2–3 mL (piston/converter)

Factors Affecting Capacity

• Barrel size: Larger pens hold more ink.
• Refill/cartridge design: Proprietary vs. standard international.
• Ink density: Oil-based inks are denser; volume ≠ writing distance directly.

Writing Distance Estimate

• Ballpoint: ~1–2 km per mL
• Rollerball/Gel: ~0.5–1 km per mL
• Fountain pen: ~0.5–1 km per mL (varies with nib width, pressure, paper)

For exact capacity, check the manufacturer's specifications for your specific pen model.