Every Klaro hygrometer ships pre-calibrated on factory equipment far more accurate than any at-home method. So before you reach for the salt and the zip-top bag, it's worth knowing two things: most "wrong" readings aren't the hygrometer's fault, and on some models recalibration is a one-shot deal. Here's how to tell the difference — and how to do the job right when it's genuinely needed.

First, make sure it's actually reading wrong

A reading that seems off is usually the air inside your humidor, not the instrument measuring it. Run through these before recalibrating:

• Uneven humidity is normal early on. A hygrometer sitting right on top of the Hydro Tray (or Hydro Channel) will read higher than the rest of the box — especially during seasoning, before your cigars are in. Readings won't fully even out until the humidor has been at least half full of cigars for a few weeks.
• Every hygrometer has a tolerance. Ours — and everyone else's — are accurate to about ±3%. Two perfectly working units can legitimately read a few points apart. A gap only matters once it's bigger than about 5%.
• Check the basics. Confirm the lid or door closes flush and the battery is fresh. A dying battery produces strange readings long before the screen goes blank.
• Dry home air is the usual suspect. Winter heating, air conditioning, and arid climates pull moisture out faster than the standard solution can replace it. If your humidor is stuck in the low 60s, that's an environment problem, not a calibration problem — our Winter + Dry Climate Solution is the fix.

The one-time caution: on some models the hygrometer can only be recalibrated once. That's why we recommend confirming it's actually reading wrong befo

The salt test: your 75% reference

Table salt dissolved in a little water settles the air around it at exactly 75% humidity — a physics constant you can trust more than any second-hand reading. Here's the full test:

1. Push the hygrometer out of your humidor from the inside with your finger.
2. Seal it in a zip-top bag with a small cap of table salt dampened with a few drops of water — damp sand texture, not soup. (A 75% Boveda pack works too.) If you have a second hygrometer, add it to the bag to confirm the reading.
3. Wait about 12 hours. The air in the bag will settle at 75%.

If the hygrometer reads 75% (or within a couple of points), it never needed calibrating — put it back and address the environment instead.

Recalibrating — only if the test failed

If the reading is genuinely off after 12 hours in the bag:

1. Open the bag and immediately press and hold the button on the back of the hygrometer for about 5 seconds.
2. The display will jump to 75% — it's now recalibrated against the salt reference.
3. Pop it back into your humidor. Done.

Timing matters: do the button-hold right after opening the bag, before room air shifts the sensor away from 75%. Waiting even a few minutes bakes an error into the calibration.

Still reading strange after all that?

A blank screen is almost always batteries — two LR44s on newer hygrometers, a single CR2032 on models made before 2026. A wildly low reading (like 20% inside a seasoned humidor) usually means the sensor got over-saturated: let it rest in open air near a fan for a few hours, then re-test. And if it still won't behave, email us with your order number — we stand behind our hygrometers and we'll make it right.