Its difficult to say when you don't have any other test kit results to test against. I'm sure they are as accurate or inaccurate as most other named hobbyist kits. My Nitrate kit would only measure 0, even in pottasium nitrate solution, but that was probably a one off. The Phosphate tester always measure my tap water at 4+, althought the water authority tell me that the local tap water is less than 2, so I guess they are an indication, if something is off the scale, or moving up or down.
