How to Read pH Strips

Co-authored by Chris Hasegawa, PhD and Amy Bobinger, BA

Last Updated: October 23, 2024 Fact Checked

If you’re interested in testing the alkalinity or acidity of a liquid, you can use pH strips to help you determine the pH level. If you’ve never used a pH strip, though, it might look like just a plain strip of paper, and the colorful chart looks like something you’d see in art class. Luckily, once you understand how the color coding works, reading a pH strip is easy!

Part 1

Part 1 of 2:

Using the pH Strips

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The pH scale covers a range of 14 numbers, where 7 is neutral. Lower numbers are more acidic, while higher numbers are more alkaline. Some strips only test a portion of that spectrum, so make sure the strips you buy cover the pH levels you want to test for.^{[1]
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Some test strips only need to be left in the test liquid for about a second, while others need about 20 seconds to produce a reading. Be sure to read the instructions to ensure that your reading will be accurate.^{[2]
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Dip one end of the test strip in the substance you want to test. You don’t need to submerge the whole strip in the test substance. Hold the strip at one end and dip the other end in the liquid, then remove it after the appropriate length of time.^{[3]
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- You can use pH strips to test the pH level of any liquid.
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Compare the color of the strip to the chart provided. Your pH strips should come with a pH color chart. When your test strip has finished reacting, hold it up to the chart and compare the color of the strip to the color chart.^{[4]
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Expert Source

Chris Hasegawa, PhD
Retired Science Professor & Dean

Expert Interview. 29 July 2021.} When you find the number associated with the color on the strip, you’ll have your pH reading.^{[5]
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- Acids are represented by warm colors, such as red and orange, while alkalines are associated with cooler colors, like blue and green.
- If you're using litmus paper, the strips will either look pink or blue.^{[6]
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  Chris Hasegawa, PhD
  Retired Science Professor & Dean
  
  Expert Interview. 29 July 2021.}
If you lose the chart that comes with your strips, or if your strips didn't come with a chart, you can look online for a universal chart. Even if you can't match your color exactly, you should get a close approximation of the pH level.

Part 2

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Knowing What to Test

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Test your tap water to make sure it’s acid neutral. Water is neutral, meaning it should have a pH balance of 7. Most drinking water falls in the range of 6.5-8.5. Test your drinking water to see if it falls within this range. If it isn't, there may be a contaminant in your water supply.^{[7]
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- A pH meter is a quick, easy way to test this. Once you put the device in your sample, the meter will tell you what the exact pH is.^{[8]
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  Chris Hasegawa, PhD
  Retired Science Professor & Dean
  
  Expert Interview. 29 July 2021.}
A swimming pool should stay at a pH balance of between 7.4 and 7.6. Add a product made with soda ash if the pool is below 7.4 and muriatic acid if it’s above 7.6.^{[9]
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Centers for Disease Control and Prevention
Main public health institute for the US, run by the Dept. of Health and Human Services

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Test the pH levels in your aquarium if you have one. The pH balance in your aquarium is critical to keeping your fish healthy. Since the pH levels of natural waters vary, it makes sense that different fish would have different pH requirements. Make sure you know the best pH range for your fish and test your water to make sure it falls within that range.^{[10]
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- There are a number of products available at pet supply stores to raise or lower the pH level of your fish tank.
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Measure the pH of your saliva to test your oral health. The average pH of saliva is around 6.7, but a normal range is anywhere from 6.2-7.6. If you measure your saliva and it is drastically different, your teeth are at a higher risk for cavities or gingivitis.^{[11]
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Cleveland Clinic
Educational website from one of the world's leading hospitals

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- Make sure you don’t eat or drink anything for about 30 minutes prior to testing your saliva, as this can throw off the reading.

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Question

How do you read a pH indicator strip?

Chris Hasegawa, PhD
Retired Science Professor & Dean
Dr. Chris Hasegawa was a Science Professor and the Dean at California State University Monterey Bay. Dr. Hasegawa specializes in teaching complex scientific concepts to students. He holds a BS in Biochemistry, a Master’s in Education, and his teaching credential from The University of California, Davis. He earned his PhD in Curriculum and Instruction from The University of Oregon. Before becoming a professor, Dr. Hasegawa conducted biochemical research in Neuropharmacology at the National Institute of Health. He also taught physical and life sciences and served as a teacher and administrator at public schools in California, Oregon, and Arizona.

Chris Hasegawa, PhD

Retired Science Professor & Dean

Expert Answer

Take a good look at the color of your strip. Then, compare it to the color guide on the box that your strip came in.

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My pH test is 5, how can I improve my test result to 7?

KnowledgeIsForever

Community Answer

A pH of 5 indicates your solution is acid and a pH of 7 means neutral. Therefore, you have to add a base. In the lab, you can do it with a sodium hydroxide solution - but be careful and always check your new pH with som more stripes or a pH meter! Keep in mind that this method is only appropriate for the lab and not aquariums (or any other systems).

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What is the normal pH of the stomach?

Han

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Gastric acid has a normal pH between 1.5 and 3.5; about as acidic as undiluted lemon juice.

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