PPM Conversion Reference Table (mg/L, %, ppb): A Detailed Guide

Accurately converting between PPM (parts per million), mg/L (milligrams per liter), percent (%), and PPB (parts per billion) is essential for laboratory work, water quality testing, environmental monitoring, and industry.

Below, you’ll find a comprehensive table, conversion formulas, step-by-step examples, and practical tips to help you make reliable conversions every time.

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PPM Conversion Reference Table

Unit	Relation to PPM	Conversion to PPM	Conversion from PPM	Example (100 ppm)
mg/L (water)	1 mg/L = 1 ppm	ppm = mg/L	mg/L = ppm	100 mg/L
% (percent)	1% = 10,000 ppm	ppm = % × 10,000	% = ppm ÷ 10,000	0.01%
ppb	1 ppm = 1,000 ppb	ppm = ppb ÷ 1,000	ppb = ppm × 1,000	100,000 ppb

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How to Use the Table

1. PPM and mg/L

• Rule: For dilute water solutions, 1 mg/L ≈ 1 ppm.
• Why: The density of water is roughly 1 kg/L, so 1 milligram of solute per liter of water means 1 part per million.

Formula:
ppm = mg/L
mg/L = ppm

Example:
If your test shows 25 mg/L of nitrate in water, that’s 25 ppm nitrate.

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2. PPM and Percent (%)

• Rule: 1% concentration is equal to 10,000 ppm.
• Why: Percentage is parts per hundred; ppm is parts per million. 1% = 1/100 = 10,000/1,000,000.

Formulas:

• To convert ppm to percent:
  % = ppm ÷ 10,000
• To convert percent to ppm:
  ppm = % × 10,000

Example:

• 50 ppm = 50 ÷ 10,000 = 0.005%
• 0.02% = 0.02 × 10,000 = 200 ppm

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3. PPM and PPB

• Rule: 1 ppm = 1,000 ppb
• Why: A billion is 1,000 times greater than a million, so 1 ppm = 1,000 ppb.

Formulas:

• To convert ppm to ppb:
  ppb = ppm × 1,000
• To convert ppb to ppm:
  ppm = ppb ÷ 1,000

Example:

• 2 ppm = 2 × 1,000 = 2,000 ppb
• 25,000 ppb = 25,000 ÷ 1,000 = 25 ppm

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More Practical Examples

Example 1: Converting mg/L to Percent

You measure 150 mg/L of calcium in your water. What is this as a percentage?

• Since 1 mg/L = 1 ppm (in water), 150 mg/L = 150 ppm
• Convert ppm to percent:
  % = 150 ÷ 10,000 = 0.015%

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Example 2: Converting Percent to PPB

A fertilizer label says it contains 0.003% iron.

• Convert percent to ppm:
  ppm = 0.003 × 10,000 = 30 ppm
• Convert ppm to ppb:
  ppb = 30 × 1,000 = 30,000 ppb

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Example 3: Converting PPB to mg/L

A lab detects 800 ppb of lead in water. What is this in mg/L?

• Convert ppb to ppm:
  ppm = 800 ÷ 1,000 = 0.8 ppm
• Since 1 ppm = 1 mg/L in water,
  mg/L = 0.8 mg/L

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Quick Conversion Formulas

• mg/L to ppm: 1 mg/L = 1 ppm (for water)
• ppm to mg/L: 1 ppm = 1 mg/L (for water)
• ppm to percent: % = ppm ÷ 10,000
• percent to ppm: ppm = % × 10,000
• ppm to ppb: ppb = ppm × 1,000
• ppb to ppm: ppm = ppb ÷ 1,000
• mg/L to ppb: ppb = mg/L × 1,000 (for water)

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Important Notes and Tips

• Water Density: These conversions assume the density of water is ~1 kg/L (valid for most drinking water, not for very salty solutions or other liquids).
• Context Matters: For gases or solids, check if conversions need to be adjusted for temperature, pressure, or sample mass.
• Always Check Units: Before calculating, make sure your numbers are in the correct units (mg/L, ppm, etc.).

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Useful Resources

• MG/L to PPM Calculator
• PPM Solution Calculator
• PPM for Water Testing

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Summary Table

Convert from	Convert to	Multiply / Divide by	Formula Example
mg/L	ppm	—	120 mg/L = 120 ppm
ppm	mg/L	—	80 ppm = 80 mg/L
ppm	percent	÷ 10,000	500 ppm = 0.05%
percent	ppm	× 10,000	0.02% = 200 ppm
ppm	ppb	× 1,000	2 ppm = 2,000 ppb
ppb	ppm	÷ 1,000	10,000 ppb = 10 ppm

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