Measure Original Gravity, Final Gravity & Fermentation Progress
A brewing hydrometer is one of the most important measuring tools for home brewing, allowing you to measure the specific gravity of beer, wine, cider and mead before, during and after fermentation.
By taking an Original Gravity (OG) reading before fermentation and a Final Gravity (FG) reading once fermentation is complete, you can monitor fermentation progress, determine when your brew has finished and calculate the approximate alcohol content of your finished drink.
Whether you're brewing your first beer or regularly making wine, cider or mead, a reliable specific gravity hydrometer takes the guesswork out of fermentation.
Why You'll Love It
- Measures specific gravity
- Take Original Gravity (OG) and Final Gravity (FG) readings
- Monitor fermentation progress
- Helps determine when fermentation has finished
- Use OG and FG to calculate approximate ABV
- Suitable for beer, wine, cider and mead
- Essential piece of home brewing equipment
- Easy to use with a suitable measuring cylinder
What Does a Brewing Hydrometer Do?
A hydrometer measures the density of a liquid relative to water.
Before fermentation, dissolved sugars increase the specific gravity of your wort or must. As yeast ferments those sugars, the gravity decreases.
Taking readings throughout fermentation therefore gives you a much better indication of fermentation progress than relying solely on airlock activity.
For home brewers, the two most important readings are:
OG – Original Gravity: Taken before fermentation begins.
FG – Final Gravity: Taken toward the end of fermentation once gravity has stabilised.
How to Use a Hydrometer
- Take a sample of your beer, wine, cider or mead.
- Transfer the sample into a suitable measuring cylinder.
- Carefully lower the hydrometer into the liquid.
- Make sure it is floating freely and not touching the sides or bottom.
- Allow it to settle.
- Read the specific gravity at the liquid level.
- Record your reading so it can be compared with later measurements.
For accurate fermentation monitoring, take an OG reading before fermentation and an FG reading when fermentation appears complete.
How to Calculate Alcohol Using a Hydrometer
A brewing hydrometer doesn't directly measure the alcohol percentage of your finished beer. Instead, the difference between your OG and FG readings can be used to estimate Alcohol by Volume (ABV).
A commonly used formula is:
ABV = (OG − FG) × 131.25
For example:
OG: 1.055
FG: 1.015
1.055 − 1.015 = 0.040
0.040 × 131.25 = 5.25% ABV
This gives an estimated finished alcohol content of approximately 5.25% ABV.
Hydrometer for Beer, Wine, Cider & Mead
This hydrometer can be used when making:
- Beer
- Home brew
- Wine
- Cider
- Mead
- Fermented beverages
A hydrometer is useful regardless of whether you're brewing from an extract kit, all-grain recipe or fermenting fruit, juice or honey.
Using a Hydrometer with a Measuring Cylinder
For the easiest reading, suspend your hydrometer in a sample of wort, beer, wine or cider using a suitable test cylinder.
A tall, narrow cylinder allows the hydrometer to float freely while reducing the amount of liquid required for each test.
Pair your hydrometer with our 100ml Plastic Measuring Cylinder or 250ml Glass Measuring Cylinder for convenient gravity testing.
Frequently Asked Questions
What is a brewing hydrometer?
A brewing hydrometer is an instrument used to measure the specific gravity of beer, wine, cider, mead and other fermenting liquids.
What is specific gravity?
Specific gravity is a measurement comparing the density of your brewing liquid with water. Dissolved sugars increase the reading, which makes specific gravity useful for monitoring fermentation.
When should I use my hydrometer?
Take an Original Gravity reading before fermentation begins and Final Gravity readings toward the end of fermentation. Stable readings over the appropriate period for your brew are a useful indication that fermentation has finished.
Can I use this hydrometer for beer?
Yes. It can be used as a beer hydrometer for checking wort gravity and monitoring fermentation.
Can I use a hydrometer for wine and cider?
Yes. Hydrometers are commonly used for beer, wine, cider and mead making.
Does a hydrometer measure alcohol?
A standard brewing hydrometer does not directly measure the alcohol percentage of finished beer. Instead, your Original Gravity and Final Gravity measurements can be used to estimate ABV.
Do I need a measuring cylinder?
You'll need a container deep and narrow enough for the hydrometer to float freely. A dedicated hydrometer or measuring cylinder makes taking readings much easier.
Why Buy from Border Brewing Supplies?
Border Brewing Supplies stocks home brewing equipment and ingredients for beer, wine, cider, mead and distilling customers throughout Australia.
Order your brewing hydrometer online Australia-wide, or Click & Collect from our Tweed Heads South store, conveniently located for home brewers across Tweed Heads, the Gold Coast and Northern NSW.
