How to Calibrate a Hygrometer: The Salt Test, Step by Step

That little gauge in your humidor is only useful if it's telling the truth — and most cheap ones don't, straight out of the box. Knowing how to calibrate a hygrometer is the one humidor skill that protects every cigar you own, and it costs you nothing but a pinch of salt and a few hours of patience. Here's the whole process.

Why an Accurate Hygrometer Matters

A hygrometer measures relative humidity — the moisture in the air inside your humidor. Cigars want to sit right around 65–70% humidity (with about 70°F temperature). Too dry and they crack and burn hot; too wet and they smoke poorly or grow mold.

The problem: a hygrometer that reads 5% or 10% off will quietly lie to you for months. You'll think you're at 68% while you're actually at 60% and slowly drying out your collection. Calibrating tells you exactly how far off the gauge is, so you can trust it. For the full picture on target ranges, see our cigar humidity guide.

How to Calibrate a Hygrometer With the Salt Test

The salt test is the classic, reliable method, and it works because a saturated salt solution always holds the surrounding air at exactly 75% relative humidity in a sealed space. That gives you a free, dependable reference point.

You'll need: table salt, water, a small bottle cap or shallow dish, and a sealable zip-top bag or airtight container.

1. Make the salt slurry. Pour a small amount of table salt into the bottle cap. Add a few drops of water — just enough to dampen it into a wet, slushy paste. It should not be soupy; you don't want standing water sloshing onto the hygrometer.
2. Seal them together. Place the cap of damp salt and your hygrometer side by side inside the zip-top bag or container. Don't let the hygrometer touch the salt. Seal it tightly so no air escapes.
3. Wait 6–8 hours. Set it somewhere at stable room temperature and leave it alone. The salt needs time to bring the trapped air to exactly 75%.
4. Read it without opening. Check the hygrometer through the bag if you can. A perfectly accurate hygrometer will read 75%.
5. Note the difference. If it reads 73%, it's running 2% low. If it reads 78%, it's running 3% high. That gap is your calibration offset.

Adjusting Your Hygrometer

What you do with that offset depends on your gauge:

• Digital with a calibration button: Many digital models have a small recessed button (often held for a few seconds) that resets the current reading to 75%. Press it while it's still sealed with the salt.
• Analog with an adjustment screw: Most dial hygrometers have a tiny screw on the back. Turn it until the needle points to 75%.
• No adjustment at all: Plenty of cheap units can't be adjusted. That's fine — just remember the offset. If it reads 2% low, add 2% to every reading from now on.

That's it. Your gauge is now honest.

A Quicker Option: Pre-Made Calibration Packs

If the salt test feels fiddly, you can buy a sealed 75% calibration pack (the same brands that make humidification packs sell them). You drop the hygrometer and the pack in a bag, wait the recommended time, and check for 75% — no measuring salt or water. It's foolproof and reusable. The salt test is free, though, and works just as well when done carefully.

Digital vs Analog Hygrometers

Should you even be using that dial gauge? Here's the honest comparison.

	Digital	Analog (dial)
Accuracy	Generally better	Drifts more over time
Readability	Clear number	Needle you estimate
Calibration	Often a button	Adjustment screw
Drift	Slower	Faster — recheck often

The short version: digital hygrometers are usually more accurate and easier to read. Analog models use a coiled metal spring that loses accuracy as it ages, so they need recalibrating more often. Either type must be calibrated to be trustworthy — but a good digital unit will hold its accuracy longer. Most cigar smokers go digital for that reason. If you're still setting up your storage, our humidor seasoning guide walks through the rest of the first-time setup, and our best humidor for beginners roundup covers what to buy if you're starting from scratch.

How Often to Recalibrate

• Digital: once or twice a year, plus any time a reading looks off.
• Analog: every few months — they drift faster.
• Brand new: always calibrate before you trust it. Factory gauges are frequently wrong.

The Recap

To calibrate a hygrometer, run the salt test: make a damp salt slurry in a cap, seal it in a bag with the hygrometer for 6–8 hours, and check for 75% relative humidity. Any difference is your offset — adjust the gauge or add the offset to future readings. An accurate hygrometer is the difference between a healthy humidor and a slow disaster, and digital models hold their accuracy best.

Once your gauge is honest, track your humidity and your whole collection in one place with the Casa DNC app.