Humidity Pack Calculator
Two-way packs are sized by the volume of air they have to hold at a setpoint, not by how many cigars are in the box. This is the single most common provisioning error: a pack count chosen from cigar count leaves large containers permanently a few points under target, and no amount of refilling fixes it because nothing is being refilled.
The coefficient below is 30 g of media per litre, calibrated against the case most people can check against their own shelf: a 50-count desktop humidor has roughly 4 L of interior space and is normally run on two 60 g packs. It is shown rather than hidden so you can disagree with it.
About 4.0 L of interior — start with
120 g
of two-way media, which is 2 × 60 g
Sized at 30 g per litre and always rounded up. Under-provisioning is the usual reason a container reads several points below target no matter what you do; over-provisioning just means the packs last longer. A leaky box, a dry winter room, or a container opened daily all justify going up a size.
Which rating to buy
Packs come rated at fixed humidities — commonly 62%, 65%, 69% and 72% — and they hold that value in both directions, releasing moisture when the air is drier and absorbing it when wetter. Buy the rating you actually want to store at, because the pack will win: putting a 72% pack in a box you intend to keep at 65% gives you a 72% box.
For most collections 62% or 65% is the sensible choice. Drier storage is materially safer — mould becomes a live risk above roughly 72%, and every point below that is margin — at very little cost. The reasoning is in humidity targets.
When to add more than the calculator says
- —A box that fails the paper seal test — leaks consume capacity continuously.
- —Winter, in a heated room. Ambient at 25% RH raises the gradient across every seam.
- —A container you open daily rather than weekly.
- —A new wooden humidor whose lining is not yet fully seasoned, which will absorb far more than the air does.
Packs need no water and should never be opened or topped up. If a box still will not hold its number after correct provisioning, the problem is elsewhere — work through raising or lowering humidor humidity in order, starting by confirming the hygrometer is not simply wrong. Related: how a reading shifts with temperature.