Being able to determine the exact pH level of your nutrient solution is important. Plants have different preferences when it comes to pH levels. Keeping these levels within the ideal ranges will allow your plants to take in all of the nutrients they need to thrive. If the pH levels drift too far from this range, nutrients will be locked out and your plants will be unable to absorb them. This can cause stunted growth, and, if left unchecked, can even kill your plants.

A pH pen is a tried-and-true piece of equipment every serious gardener should own and know how to use. The key to keeping your garden’s pH levels in the ideal range is testing your nutrient solution or water runoff often with a reliable, calibrated pH pen.

What You’ll Need to Calibrate a pH Pen Successfully

  • pH pen
  • pH calibration solution (pH 4, pH 7 and pH 10)
  • Small measuring cups
  • Distilled water
  • Gloves
  • A small screwdriver for manually calibrated pH pens

Digital pH Pens

Most pH pen brands generally use the same method of calibration. With gloves on, pour a small amount of each type of room-temperature calibration solution into small measuring cups. Use one cup for pH 4, one cup for pH 7, and one cup for pH 10.

Always use the freshest possible solution for the most accurate results, and always start with a clean probe. Digital pens usually have a calibration setting that will prompt you to submerge the probe end of your pH pen in the different calibration solutions. pH 4 is usually prompted first, followed by pH 7 and pH 10.

Submerge the probe end of the pH pen in your pH 4 solution. You may have to hold your calibration button down for a few seconds. Check your user manual for exact directions. Once your pH pen is calibrated to pH 4, repeat the process with the pH 7 and pH 10 solutions, rinsing the probe end with distilled water between each step.

Not all brands of pens will require all three pH solutions for calibrating, and even if they, do you don’t have to do this each time, but the more points your pen is calibrated to, the more accurate it will read.

Manually Calibrated pH Pens

Some pH pens require manual calibration. On these types of pens, there will be a screw, usually on the butt end of the pen, which is used to change the reading on the face of the pen. Use the exact same process as previously mentioned for the digital pH pens simply by turning the screw/dial to line up the pH.

The more often you calibrate your pH pen, the more accurate it will read. The average gardener needs to calibrate their pH pen every 2-3 feedings. Accurate pH readings take the guess work out of gardening and increase your chances of growing success.