Help - My pH pen won't calibrate

Is your Bluelab pH Pen not calibrating in pH7 and pH4 solutions? Check here how it’s done correctly.

The first step is to always make sure the glass tip of the pen/probe is well hydrated and clean.

More information on how to hydrate and clean your pen/probe, can be found at the bottom of this page.


After cleaning, proceed with a two-point calibration according to the steps below:


Set-up required prior to calibration:

  • Pour fresh pH7.0 solution into a cup (enough to submerge the glass tip of your pen/probe, and ensure solution has not expired).
  • Pour fresh pH4.0 or pH10.0 solution into a cup.
  • Tap water is necessary for rinsing your pen/probe.
  • Paper towels are optional, for drying off excess water (or just shake the excess water off the pen/probe).

Press “Power/Hold” button to turn on the device. The pen has an auto-off function after 4 minutes.



Place probe tip in pH7.0 (calibration order should always start with 7 first!).

Wait for your pH reading to stabilize. 

Long press “cal” button, until “CAL” is displayed on screen. Release button. Let the 0-sequencing runs its course, and when the “0000” stops flashing, the first point calibration is complete. 

A reading of 7.0 will be displayed on screen, the accuracy of our pens/probes is plus or minus 0.1pH. 



After calibrating in pH7.0, rinse the probe tip in tap water then gently shake off or wipe off any excess water with a paper towel.


pH4.0 (or 10.0) SOLUTION

Place probe tip in pH4.0.

Wait for your pH reading to stabilize (note your pH reading should be close to 4.0, but may not be exact before calibrating). 

Long press “cal” button, "CAL" will be displayed on screen. Release the button and the pen will continue calibrating to pH4.0.



After completing the calibration in pH 4 or 10, a checkmark (tick mark) will be displayed at the bottom of the screen. This indicates that the calibration has been successful. This mark will disappear after 30 days, indicating that re-calibration is required. 



Make sure to keep the pH probe tip (glass bulb) hydrated in KCl solution.

For other tips, consult the manual below.


Bluelab pH Pen Manual (click on magnifying glass to adjust zoom)

Prefer to watch the video instead?



It is recommended to hydrate a pH probe by submerging the glass tip in KCl storage solution for 24 hours before use.

WARNING: Never use RO, Deionized or Distilled water for storage or hydration. Pure water changes the chemistry in the probe reference, causing the probe to die.

You can purchase the Bluelab Calibration Solutions here.



Bluelab pH Pen Care & Cleaning Information Sheet  (click on magnifying glass to adjust zoom).


You can purchase the Bluelab pH Pen Care & Cleaning Kit here.