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Hydrometer vs refractometer: which to use and when

A floating glass tube or a few drops on a prism. Both read gravity; only one reads finished beer without a formula.

Updated November 2026 · 6 min read

Refractometer with the daylight plate open and an inset of its reading scale
FastRack Triple Scale HydrometerSOLIGT Triple Scale Hydrometer & Glass Test Jar KitBrewing America Triple Scale Hydrometer & Test Jar (USA-Made)North Mountain Supply 8" Italian Glass Triple Scale HydrometerCraft A Brew Polycarbonate Triple Scale HydrometerV-Resourcing Beer Wort Refractometer (Brix/SG)
Photo: Fernando G. ( FGM ), CC BY-SA 3.0, via Wikimedia Commons
The short version
  • Hydrometer: measures density directly. Reads original and final gravity with no formula, but needs a test jar full of sample and a temperature correction (most are calibrated at 60°F or 68°F).
  • Refractometer: measures how a few drops bend light, shown in Brix. Perfect for wort on brew day; after fermentation starts, alcohol skews the reading, so use a correction formula.
  • Common dual-scale refractometers list Brix 0–32% and SG 1.000–1.130 with ATC between 10–30°C; triple-scale hydrometers list SG 0.990–1.170.
  • Most brewers own both: a refractometer for brew-day checks, a hydrometer to confirm final gravity before bottling.

Hydrometer vs refractometer is a question about when you measure. A hydrometer floats higher in denser liquid, so it reads specific gravity (SG) directly at any stage, including finished beer, wine, cider and mead. A refractometer reads the refractive index of a few drops, calibrated to sugar in water (Brix), which is ideal for unfermented wort but misleading once alcohol is present.

This page compares the two on range, accuracy, sample size, temperature handling and the post-fermentation problem, with picks from FastRack, SOLIGT, Brewing America, North Mountain Supply, Craft A Brew, V-Resourcing, Tiaoyeer, Milwaukee, Atago and Anton Paar. See every meter in the hydrometers and meters hub.

Hydrometer

Floats in a test jar; reads specific gravity directly before and after fermentation

Browse
vs

Refractometer

Two or three drops; fast wort readings, needs correction once alcohol is present

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Picks from each side

Hydrometer

Refractometer

Hydrometer vs refractometer side by side

HydrometerRefractometer
What it measuresDensity (specific gravity)Refractive index, shown as Brix (some add an SG scale)
SampleEnough to float it in a test jar2–3 drops (listing)
Typical listed rangeSG 0.990–1.170 (triple scale)Brix 0–32%, SG 1.000–1.130
Reads finished beer or wine directly✓✗ Needs an alcohol correction
Temperature handling~ Correct to the calibration temp (60°F or 68°F)✓ ATC on most models, 10–30°C
Reads hot wort quickly✗ Cool the sample first✓ Drops cool in seconds
Breakage~ Glass (polycarbonate options exist)✓ Sturdy body
Wort correction factorNot needed~ About 1.04 (adjustable)

Source: Listings for the meters shown; Sean Terrill refractometer notes; Brewer's Friend ABV calculator

Ranges and resolution compared

Top of the listed scale

Brix for refractometers (SG ~1.130 ≈ 31 Brix; wine and mead musts often need more)

Dual-scale analog (V-Resourcing, Tiaoyeer)Dual-scale analog (V-Resourcing, Tiaoyeer): 32 Brix32 BrixFastRack hydrometer (Balling scale)FastRack hydrometer (Balling scale): 35 Brix35 BrixAtago PAL-1 digitalAtago PAL-1 digital: 53 Brix53 BrixMilwaukee MA871 digitalMilwaukee MA871 digital: 85 Brix85 Brix
Source: Listings for each meter
±0.2% BrixListed accuracy, Tiaoyeer, V-Resourcing and Milwaukee MA871
±0.001 SGListed SG accuracy, V-Resourcing wort refractometer
±0.04 BrixAnton Paar SmartRef, per maker

For beer, a 0–32 Brix analog refractometer covers every normal wort. For big wines, meads and dessert musts above about 1.130, a hydrometer reaching 1.170 or a digital refractometer with a wider Brix range is the safer choice. Hydrometer accuracy is rarely listed; Brewing America describes its hydrometer as NIST-traceable per the maker.

Hydrometers differ mostly in build and extras. The SOLIGT and Brewing America sets include a test jar, which you need anyway; the North Mountain Supply model is Italian glass and lead- and mercury-free per its listing; and the Craft A Brew polycarbonate hydrometer trades a little readability for not shattering on a tile floor. Refractometers split into analog dual-scale models, which you hold up to the light and read through an eyepiece, and digital models (Atago, Milwaukee, Anton Paar) that show a number on a screen and remove the guesswork of reading a blurry line. The Anton Paar SmartRef also logs readings to an app over Bluetooth.

Why refractometers read wrong after fermentation

Alcohol bends light more than water does, while it makes the liquid less dense. So once fermentation starts, a refractometer reads a Brix value that's too high, and converting it straight to SG overstates the final gravity. The fix is a correction formula that uses the original Brix and the current Brix together. Sean Terrill's cubic formula is the one most calculators use, and the refractometer mode in our ABV calculator applies it (marked as an approximation).

  1. Calibrate

    Put 2–3 drops of deionized water on the prism and set zero, at room temperature.

  2. Read original gravity

    Take a wort sample before pitching; divide Brix by the wort correction factor (about 1.04) or let the calculator do it.

  3. Read during or after fermentation

    Enter both the original and the current Brix in the corrected formula. Don't convert the second reading on its own.

  4. Confirm with a hydrometer

    Before bottling, a hydrometer check removes any doubt about final gravity.

    FastRack Triple Scale HydrometerSOLIGT Triple Scale Hydrometer & Glass Test Jar Kit

Temperature: correction vs ATC

Hydrometers are calibrated at one temperature, usually 60°F (15.6°C) or 68°F (20°C), printed on the instrument. A sample at 80°F reads low; the ABV calculator's hydrometer correction adjusts it. Refractometers listing ATC compensate automatically within their range (10–30°C, about 50–86°F, on the listed dual-scale models), and the tiny sample cools in seconds, which is why they're handy at the kettle.

Hydrometer jar tipSpin the hydrometer to knock off bubbles, read at the bottom of the meniscus at eye level, and never return a sample to the fermenter.

When each one is the right tool

  • Pre-boil gravity on brew day: refractometer. Two drops, ATC, no waiting; fix volume or gravity with the dilution and boil-off calculator.
  • Original gravity after chilling: either. Many brewers use both to check the wort correction factor.
  • Is fermentation finished? hydrometer, or a refractometer with the corrected formula. Bottle only after 2–3 equal readings over 2–3 days.
  • Wine, cider and mead: hydrometer, since must gravities and finished dry wines (below 1.000) are outside many refractometer scales.
  • Continuous logging: a floating digital hydrometer; see Tilt vs RAPT Pill vs iSpindel.
Refractometer prism and cover plate, where a drop of wort goes
A refractometer needs only a few drops on the prism.Photo: CEphoto, Uwe Aranas, CC BY-SA 3.0, via Wikimedia Commons

Write every reading in the brew-day log so the ABV summary has numbers to work with.

Who should choose which

You…HydrometerRefractometer
Are buying your first gravity meter✓~
Brew all-grain and check pre-boil gravity~✓
Make wine, cider or mead✓~
Want to waste less beer per reading✗✓
Want one reading with no formula at the end✓✗
Have a strong must above 1.130✓~ Digital models only

Buy a hydrometer first (with a test jar) if you brew extract kits, wine, cider or mead: it reads every stage directly. Add a refractometer when you go all-grain and want quick pre-boil and OG readings. If you only ever buy one, the hydrometer is the one that can't mislead you at bottling time. Our first brew day page lists it with the rest of the essentials.

Mistakes to avoid

  1. Converting a post-fermentation refractometer reading to SG directly. It reads high; use the corrected formula.
  2. Reading a hot sample with a hydrometer. Cool it or correct for temperature.
  3. Skipping refractometer calibration. Zero it with deionized water at room temperature each session.
  4. Reading a hydrometer with bubbles clinging to it. Spin it and wait a moment.
  5. Bottling on one low reading. Wait for 2–3 identical readings over 2–3 days to avoid bottle bombs.
Avoid bottle bombsBottle only after the gravity reads the same 2–3 days in a row, measure priming sugar with a calculator, use standard bottles only to about 3 volumes, store them in a closed box at room temperature and refrigerate once carbonated.Source: BYO carbonation priming chart
Verdict

A hydrometer is the essential first meter: it reads gravity directly from wort to finished wine with only a temperature correction. A refractometer is the brew-day upgrade for fast, two-drop readings of unfermented wort, and it needs a corrected formula once alcohol is present. Most all-grain brewers end up owning both.

How we chose

We compared the listed ranges, scales, accuracy and ATC ranges of the meters shown, plus published correction methods (Sean Terrill; Brewer's Friend). We did not calibrate or test these instruments.

ABV calculatorWork out ABV from OG and FG with the standard and high-gravity formulas, hydrometer temperature correction,…Dilution and boil-off calculatorDilute wort to a target gravity, and work out pre-boil volume from your boil-off rate, boil time and losses,…Printable brew-day log and recipe sheetFree brew-day log: record recipe, water and salts, mash, gravities, yeast, fermentation temperatures,…

Questions

Hydrometer vs refractometer: which is more accurate?
Both are accurate for unfermented wort when calibrated: listed dual-scale refractometers give ±0.2% Brix (about ±0.001 SG). After fermentation starts, a hydrometer is more reliable because a refractometer needs an alcohol-correction formula.
Is a refractometer accurate after fermentation?
Not on its own. Alcohol makes it read high. Enter the original and current Brix into a corrected formula, such as the refractometer mode in our ABV calculator, and confirm final gravity with a hydrometer before bottling.
What is the wort correction factor?
Refractometers are calibrated to sucrose in water, and wort reads slightly differently. Dividing the Brix reading by about 1.04 corrects it; you can measure your own factor by comparing hydrometer and refractometer readings of the same wort.
Do I need to correct hydrometer readings for temperature?
Yes, if the sample isn't at the hydrometer's calibration temperature (usually 60°F or 68°F). The ABV calculator has a hydrometer temperature correction.
Can I use a refractometer for wine?
For grape or fruit must before fermentation, yes, if the must is within its range. For finished wine below 1.000 SG and high-sugar musts, a hydrometer is the better tool.
How do I read a hydrometer?
Fill the test jar, float the hydrometer, spin it to remove bubbles and read the scale at the bottom of the curved surface at eye level, then correct for temperature.

Sources

  1. Sean Terrill: Refractometer FG results and correction
  2. Brewer's Friend: ABV calculator
  3. Craft Beer & Brewing: Tools (hydrometer correction, SG/Plato)
  4. John Palmer, How to Brew (online edition)