# What are some common Hardness unit conversions?

## Document ID

Document ID TE781

## Published Date

Published Date 07/09/2020
Question
What are some common Hardness unit conversions?
Summary
Converting Hardness
The table below shows the factors to convert hardness from one unit of measure to another. For example, to convert mg/L CaCO3 to German parts/100,000 CaO, multiply the value in mg/L x 0.056.
To convert from mg/L to grains per gallon, multiply by 17.1.
Note: meq/L = N × 1000

Units of measure mg/L
CaCO3
British
gr/gal
(Imperial)
CaCO3
American
gr/gal
(US)
CaCO3
French parts/
100,000 CaCO3
German parts/
100,000 CaO
meq/L g/L CaO lb/ft3
CaCO3
mg/L CaCO3 1.0 0.07 0.058 0.1 0.056 0.02 5.6x10–4 6.23x10–5
English gr/gal
CaCO3
14.3 1.0 0.83 1.43 0.83 0.286 8.0x10–3 8.9x10–4
US gr/gal CaCO3 17.1 1.2 1.0 1.72 0.96 0.343 9.66x10–3 1.07x10–3
French
p/100,000 CaCO3
10.0 0.7 0.58 1.0 0.56 0.2 5.6x10–3 6.23x10–4
German
p/100,000 CaO
17.9 1.25 1.04 1.79 1.0 0.358 1x10–2 1.12x10–3
meq/L 50.0 3.5 2.9 5.0 2.8 1.0 2.8x10–2 3.11x10–2
g/L CaO 1790.0 125.0 104.2 179.0 100.0 35.8 1.0 0.112
lb/ft3 CaCO3 16,100.0 1123.0 935.0 1610.0 900.0 321.0 9.0 1.0