Here are links to some free Online Brewing Calculators

 Brewers Friend:

General Calculators 
Complete Beer Recipe Builder
ABV- Alcohol by Volume –  If you took an original gravity reading (or had estimated OG), and also took a final gravity (FG) reading prior to adding priming sugar bottling you can find out your batch’s alcohol by volume ABV.
Hydrometer Temperature
IBU Calculator – Bitterness
SRM Calculator – Color
Dilution & Boil Off Gravity Calculator
Yeast Pitch Rate & Starter Calculator
Refractometer Calculator
Brix Converter
Chaptalization Calculator

All Grain Brewers Calculators
Mash Calculator
All Grain OG/FG
This calculator is designed to work with this All Grain Brew Sheet
Water Chemistry Basic
Water Chemistry Advanced
Brewhouse Efficiency
Quick Infusion Calculator

Extract Brewers Calculator
Extract OG/FG
This Calculator designed to work with this Extract Brew Sheet

Bottling, Priming and Kegging Calculators
Bottling Calculator
Priming Calculator
Keg Carbonation Calculator
Gyle & Krausen Priming calculator

‘BREW YOUR OWN’ website links

Hops Alpha Acid table
Compare and select Hops based on Alpha Acid, and Flavor Description and review possible Hop substitutions.
Grains and Adjuncts Chart
Composite list of grains and adjuncts. The color is listed in degrees Lovibond and the gravity is calculated from 1 pound of the ingredient in 1 gallon of water. Click on the general categories below to begin experimenting and enjoy!
Homebrew Yeast Strains Chart
Choosing the proper yeast strain is essential to the quality of your finished beer. The Chart is an overview of the most common strains currently available to homebrewers from North America’s leading suppliers, who provided all of the information for this chart. Just select a beer style from the menu below to view a chart with appropriate yeast strains to consider for your recipe.
Pitching rates for Fresh Yeast charts
Troubleshooting Chart