Water Treatment Unit Converter — Free Tools

Hardness

All units convert from ppm as CaCO₃ (base unit). Enter any value to update all others.

ppm as CaCO₃ (mg/L as CaCO₃)

ppm

mg/L as Ca²⁺

mg/L

mEq/L

mmol/L (as Ca²⁺)

mmol/L

French degrees (°f)

°f

German degrees (°dH)

°dH

Clark / English (°e)

°e

Grains per gallon (gpg)

gpg

1 gpg = 17.12 mg/L as CaCO₃. French degrees = mg/L ÷ 10.

Alkalinity

All units convert from ppm as CaCO₃ (base unit). Enter any value to update all others.

ppm as CaCO₃ (mg/L as CaCO₃)

ppm

mg/L as HCO₃⁻

mg/L

mg/L as CO₃²⁻

mg/L

mEq/L

French degrees (°f)

°f

German degrees (°dH)

°dH

Grains per gallon (gpg)

gpg

For mixed HCO₃⁻/CO₃²⁻/OH⁻ alkalinity, use P- and M-alkalinity titration. This converter assumes all alkalinity as bicarbonate (most common for natural waters).

Flow Rate

All units convert from GPM (base unit). Enter any value to update all others.

GPM (US gallons per minute)

GPM

MGD (million gal/day)

MGD

m³/hr

m³/day

L/min

L/s

L/hr

Barrels/day (42 gal)

bbl/day

ft³/min (CFM)

CFM

Acre-feet/day

ac-ft/day

GPH (gallons per hour)

GPH

GPD (gallons per day)

GPD

Pressure

All units convert from psi (base unit). Enter any value to update all others.

psi

bar

kPa

MPa

atm

mmHg (Torr)

mmHg

in H₂O (at 60°F)

in H₂O

ft H₂O (at 60°F)

ft H₂O

kg/cm² (kgf/cm²)

kgf/cm²

Temperature

Edit any field — all others update instantly using exact offset formulas.

°F (Fahrenheit)

°F

°C (Celsius)

°C

K (Kelvin)

°R (Rankine)

°R

Pure water boils at 212°F / 100°C / 373.15 K. Freezes at 32°F / 0°C / 273.15 K.

Concentration

All units convert from mg/L (base unit). Enter any value to update all others.

mg/L (ppm)

mg/L

ppb (µg/L)

µg/L

g/L

% w/v

Grains/gal

gr/gal

mg/dL

µg/mL

ppt (parts per trillion)

ppt

For dilute solutions (<10,000 mg/L), density ≈ 1 g/mL, so ppm ≈ mg/L. For concentrated solutions or brines, use weight-to-weight percent with actual density.

TDS / Conductivity

Base unit: EC (µS/cm). Two TDS conversion factors shown simultaneously.

EC (µS/cm)

µS/cm

mS/cm

TDS (ppm, factor 0.50 — YSI/Hach)

ppm

TDS (ppm, factor 0.64 — ISO/European)

ppm

Resistivity (MΩ·cm)

MΩ·cm

Pure water at 25°C: 0.0551 µS/cm = 18.18 MΩ·cm

The 0.50 factor (YSI/Hach) and 0.64 factor (ISO/European) are both widely used. For accurate TDS measurement in seawater or industrial brines, use direct gravimetric analysis.

Specific Ions

Convert individual ion concentrations between ppm-as-ion and ppm-as-CaCO₃. Each row is independent — edit either field to update the other.

Ion

ppm as ion (mg/L)

ppm as CaCO₃

These conversions use 50.04 as the equivalent weight of CaCO₃ (MW 100.09 / 2). Formula: ppm as CaCO₃ = ppm as ion × (50.04 / equivalent weight).

Volume

All units convert from US gallons (base unit). Enter any value to update all others.

US gallons

US gal

Imperial gallons

Imp. gal

Liters

m³

ft³

Barrel (42 US gal)

bbl

Acre-foot

ac-ft

Milliliters

Fluid ounces (US)

fl oz

Cups (US)

cups

Cubic inches

in³

Length / Pipe

Basic length conversion plus ANSI pipe dimension reference.

Inches

Millimeters

Centimeters

Feet

Meters

Yards

Pipe Dimension Reference — ANSI B36.10 (Schedule 40)

NPS (in)	OD (in)	ID Sch40 (in)	Wall Sch40 (in)	Flow Area (in²)
0.5	0.840	0.622	0.109	0.304
0.75	1.050	0.824	0.113	0.533
1	1.315	1.049	0.133	0.864
1.25	1.660	1.380	0.140	1.495
1.5	1.900	1.610	0.145	2.036
2	2.375	2.067	0.154	3.355
2.5	2.875	2.469	0.203	4.788
3	3.500	3.068	0.216	7.393
4	4.500	4.026	0.237	12.730
6	6.625	6.065	0.280	28.890
8	8.625	7.981	0.322	50.027
10	10.750	10.020	0.365	78.854
12	12.750	11.938	0.406	111.93

Chlorine Dose

Enter flow rate and chlorine dose — all mass rates update instantly.

Chlorine dose

mg/L

Flow rate

GPM

Output Value

Dose (lbs/day) —

Dose (kg/day) —

NaOCl feed (12.5%, GPD) —

NaOCl feed (12.5%, mL/min) —

Cl₂ gas (lbs/day) —

Formula: lbs/day = flow (MGD) × dose (mg/L) × 8.34. NaOCl 12.5% (SG = 1.16): divide lbs/day by 1.211 for GPD feed. Cl₂ gas = 100% active Cl, equals dose in lbs/day.