Question 1

Why is 1% = 10,000 ppm?

Accepted Answer

1% by weight = 1 part in 100 = 10,000 parts per million. The math is exact for dilute aqueous solutions.

Question 2

Is ppm always mg/L?

Accepted Answer

In water yes — because 1 L of water weighs about 1 kg. In other media (air, soil) different conversions apply.

Question 3

What's a ppb?

Accepted Answer

Parts per billion. 1 ppb = 1 µg/L = 0.001 mg/L. EPA lead action level is 15 ppb in tap water.

Question 4

When do plants use percent vs ppm?

Accepted Answer

Bulk chemicals (12.5% NaOCl, 50% NaOH, 23% fluorosilicic acid) by percent. Treatment doses, residuals, and compliance limits by mg/L (ppm).

ppm ↔ Percent (%) Concentration Converter