mg/l to lb/gal Converter

A level of 100 mg/L is about 0.000835 pounds per US gallon.

The mg/L to lb/gal formula

Pounds per gallon equal mg/L times 3.785411784, divided by 453,592.37.

The first number is litres per US gallon and the second is milligrams per pound.

Take 100 mg/L. 100 × 0.000008345404 gives 0.000835 lb/gal.

Take 1,000 mg/L. 1,000 × 0.000008345404 gives 0.008345 lb/gal.

Two unit changes at once

A US gallon is defined as exactly 3.785411784 litres (Wikipedia: Gallon). A pound is defined as exactly 453.59237 grams, which is 453,592.37 milligrams (ProofWiki: Pound Avoirdupois).

So the factor is about 0.000008345 pounds per gallon for each mg/L.

How to convert mg/L to lb/gal step by step

1. Read the concentration in mg/L.
2. Multiply it by 3.785411784 to get milligrams per US gallon.
3. Divide by 453,592.37 to change milligrams into pounds.
4. Read pounds per 1,000 gallons in the last column.

Round only at the end. Rounding in the middle of a sum adds small errors that grow.

mg/L to lb/gal conversion table

The highlighted row is the default of the calculator. The last column gives Pounds per 1,000 US gallons.

A quick mental shortcut for mg/L to lb/gal

Remember 8.345. One mg/L is about 8.345 pounds in a million US gallons.

So 2 mg/L in a million gallons needs about 16.7 pounds.

Pounds per million gallons

Water works often use pounds per million gallons. One mg/L is about 8.345 pounds per million US gallons.

Multiply the mg/L by 8.345 to get the pounds in a million gallons.

A dosing example

To raise a tank of 10,000 US gallons by 3 mg/L, you need about 3 times 8.345 divided by 100, which is about 0.25 pounds of the pure substance.

Real products are not pure, so check the label for strength.

US and imperial gallons

The US gallon is 3.785 litres and the imperial gallon is 4.546 litres (Wikipedia: Gallon).

This page uses the US gallon.

Safety with chemicals

Follow the product label and local rules when you dose water. Too much of some chemicals can be harmful.

If you are unsure, ask a qualified water treatment operator.

Quick conversion answers

Where this conversion is used

Pool and water treatment staff change a dose in mg/L into pounds for a tank.

Engineers compare metric and US units on a water report.

Common mistakes to avoid

• Using the imperial gallon. The factor would be wrong by about 20 percent.
• Mixing pounds per gallon with pounds per 1,000 gallons. Check the column.
• Treating the answer as product weight. It is the weight of the pure substance.
• Dividing instead of multiplying. Pounds per gallon is a small number.

Related converters

• mg/L to pounds
• mg/L to ppm
• mg/L to percent
• mg/L to ug

More values at a glance

2 mg/L is 0.00001669 lb/gal. 30 mg/L is 0.0002504 lb/gal. 75 mg/L is 0.0006259 lb/gal.

150 mg/L is 0.001252 lb/gal. 300 mg/L is 0.002504 lb/gal. 400 mg/L is 0.003338 lb/gal.

1,500 mg/L is 0.01252 lb/gal. 2,500 mg/L is 0.02086 lb/gal. 20,000 mg/L is 0.1669 lb/gal.

Common dosing levels

0.5 mg/L is 0.004173 lb per 1,000 gal. 1 mg/L is 0.008345 lb per 1,000 gal. 2 mg/L is 0.01669 lb per 1,000 gal.

5 mg/L is 0.04173 lb per 1,000 gal. 10 mg/L is 0.08345 lb per 1,000 gal. 25 mg/L is 0.2086 lb per 1,000 gal.

50 mg/L is 0.4173 lb per 1,000 gal. 500 mg/L is 4.173 lb per 1,000 gal. 1,000 mg/L is 8.345 lb per 1,000 gal.

More dosing examples

Use the 8.345 rule to check your work. A level of 20 mg/L in a million US gallons is about 166.9 pounds. A level of 250 mg/L is about 2,086 pounds per million gallons.

For a smaller tank of 10,000 US gallons at 20 mg/L, divide 166.9 by 100. That gives about 1.669 pounds of the pure substance.

Round the final figure only at the end. Early rounding can move the answer by a few percent on large tanks.

Frequently asked questions

Sources

• Wikipedia: Gallon (en.wikipedia.org)
• ProofWiki: Pound Avoirdupois (proofwiki.org)