TL;DR
A hydrometer is the most fundamental measurement tool for any brewer or winemaker. Triple-scale hydrometers (SG, Brix, potential alcohol) cost 8–15 EUR and suit most homebrewers perfectly. Precision hydrometers with narrow SG ranges (e.g., 1.000–1.070) offer 0.001 resolution for advanced brewers. Thermohydrometers combine a thermometer and hydrometer in one instrument, eliminating a step. Budget 10–20 EUR for a solid triple-scale, 25–40 EUR for a precision model, or 35–60 EUR for a thermohydrometer. Always calibrate with distilled water before first use.
Why You Still Need a Hydrometer
In an age of digital refractometers, electronic density meters, and smartphone apps, the humble glass hydrometer remains the gold standard for homebrewers. Here is why:
- Accuracy: A quality hydrometer reads to ±0.001 SG (1 gravity point) — sufficient for all homebrewing purposes.
- No post-fermentation correction needed: Unlike refractometers, hydrometers give accurate readings in the presence of alcohol.
- Simplicity: No batteries, no firmware updates, no calibration drift over time.
- Cost: Under 15 EUR for a model that will last years.
- Universality: Works for beer, wine, mead, cider, kombucha, and any other fermented beverage.
The main downsides are that hydrometers require a relatively large sample (100–200 ml), are fragile (glass breaks), and need temperature correction for accurate readings — which we cover in our Gravity Temperature Correction Guide.
Types of Hydrometers
1. Triple-Scale Hydrometer
The most popular choice for homebrewers. Displays three scales simultaneously:
| Scale | Range (typical) | Resolution | Use |
|---|---|---|---|
| Specific Gravity | 0.990–1.170 | 0.002 | Primary measurement |
| Brix / Balling | 0–35+ °Bx | 0.5 °Bx | Sugar content |
| Potential Alcohol | 0–20% | 0.5% | Quick ABV estimate |
Pros: One instrument covers all bases. Affordable. Widely available.
Cons: The wide SG range means the scale is compressed — each graduation represents 0.002, making it hard to read to 0.001 precision. The potential alcohol scale is based on a simplistic formula and should not be trusted for anything beyond rough estimation.
Best for: Beginning to intermediate homebrewers, anyone who wants a single do-it-all instrument.
2. Precision (Narrow-Range) Hydrometer
These cover a narrower SG range with finer graduations:
| Model Type | Range | Resolution | Best For |
|---|---|---|---|
| Brewing range | 1.000–1.070 | 0.001 | Most beers |
| High-gravity range | 1.060–1.130 | 0.001 | Strong ales, wine, mead |
| Finishing range | 0.990–1.020 | 0.001 | Final gravity readings |
| Wine range | 0.980–1.170 | 0.002 | Full winemaking range |
Pros: Easier to read accurately. True 0.001 precision. Less parallax error.
Cons: You may need two or three to cover the full brewing range. More expensive per unit. Specialty items, harder to find locally.
Best for: Experienced brewers who want maximum accuracy, competition brewers, anyone who has struggled to read a triple-scale hydrometer precisely.
3. Thermohydrometer
A hydrometer with a built-in thermometer — typically a mercury or spirit column embedded in the stem or bulb.
| Feature | Specification |
|---|---|
| SG range | Typically 1.000–1.070 or 0.990–1.120 |
| SG resolution | 0.001 |
| Thermometer range | 0–50 °C (32–122 °F) |
| Thermometer resolution | 0.5–1.0 °C |
Pros: Simultaneous gravity and temperature reading from one instrument, one sample. Reduces equipment clutter. Makes temperature correction seamless.
Cons: More expensive. If either the hydrometer or thermometer function is damaged, you lose both. Often only available in narrower SG ranges.
Best for: Brewers who want streamlined measurement and always apply temperature correction.
4. Saccharometer (Plato Hydrometer)
Used primarily in professional brewing, these read directly in degrees Plato rather than SG. The conversion is approximately:
°P ≈ (SG − 1) × 1000 / 4
| Feature | Specification |
|---|---|
| Range | 0–30 °P (typical) |
| Resolution | 0.1 °P |
| Calibration temp | Usually 20 °C |
Best for: Professional brewers, those following European brewing literature that uses Plato exclusively.
What to Look for When Buying
1. Range and Resolution
Match the range to what you brew:
| What You Brew | Recommended Range | Minimum Resolution |
|---|---|---|
| Session beers (< 5%) | 1.000–1.070 | 0.002 (triple), 0.001 (precision) |
| General homebrewing | 0.990–1.120 | 0.002 |
| High-gravity & wine | 0.990–1.170 | 0.002 |
| Competition brewing | 1.000–1.070 + 0.990–1.020 | 0.001 |
2. Calibration Temperature
Most hydrometers sold in North America are calibrated at 15.6 °C (60 °F). European models typically use 20 °C (68 °F). This is not a quality difference — just make sure you know which standard your hydrometer uses so you apply the right correction.
3. Glass Quality and Length
- Borosilicate glass is more thermal-shock resistant than soda-lime glass. It does not matter for room-temperature samples, but matters if you accidentally dip it in hot wort.
- Length affects both resolution (longer stem = more spread-out scale) and practicality (needs a taller test jar). Standard homebrew hydrometers are 25–30 cm (10–12 in) long. Precision models can be 35 cm (14 in) or more.
4. Ballast Type
The weight in the bulb is usually lead shot or steel shot. Both work fine. Some newer models use non-toxic alternatives. This only matters if you break the hydrometer into your wort — which should not happen if you use a test jar.
5. Scale Legibility
Look for: - Black markings on a white background (avoid coloured scales — they are harder to read). - Numbered every 0.010 at minimum. - Major graduations every 0.002 or 0.001. - A paper scale sealed inside the stem, not printed on the outside (external printing wears off).
ABV CalculatorCalculate your alcohol by volume from gravity readings
Recommended Models by Category
Budget: Under 15 EUR
| Model | Type | Range | Resolution | Cal. Temp | Price |
|---|---|---|---|---|---|
| Generic Triple-Scale (various brands) | Triple | 0.990–1.170 | 0.002 | 15.6 °C | 5–10 EUR |
| Alla France 00200 | Standard | 1.000–1.100 | 0.001 | 20 °C | 12–15 EUR |
The generic triple-scale hydrometer is the workhorse of homebrewing. Quality varies between manufacturers — look for sealed internal paper scales and consistent ballast. Test with distilled water upon arrival.
Mid-Range: 15–35 EUR
| Model | Type | Range | Resolution | Cal. Temp | Price |
|---|---|---|---|---|---|
| Stevenson Reeves Precision | Precision | 1.000–1.070 | 0.001 | 20 °C | 20–30 EUR |
| Brew Perfect Thermohydrometer | Thermo | 1.000–1.070 | 0.001 | 20 °C | 30–35 EUR |
| Alla France Precision Set (2 pcs) | Precision | 1.000–1.070, 1.060–1.130 | 0.001 | 20 °C | 25–35 EUR |
A pair of precision hydrometers covering 1.000–1.070 and 1.060–1.130 will handle everything from light lagers to imperial stouts and meads. The overlapping range at 1.060–1.070 lets you cross-check readings.
Premium: 35–60+ EUR
| Model | Type | Range | Resolution | Cal. Temp | Price |
|---|---|---|---|---|---|
| H-B Durac Thermohydrometer | Thermo | 1.000–1.070 | 0.001 | 20 °C | 45–60 EUR |
| Stevenson Reeves Certified | Precision | Various | 0.0005 | 20 °C | 50–70 EUR |
The H-B Durac brand (by SP Scienceware) manufactures laboratory-grade instruments. A certified precision hydrometer with NIST-traceable calibration is overkill for homebrewing but invaluable for professional breweries needing audit-ready documentation.
Essential Accessories
Test Jar
A test jar is not optional — it is essential. Never drop your hydrometer into the fermenter.
| Feature | Recommendation |
|---|---|
| Material | Clear plastic (polycarbonate) or glass |
| Diameter | 35–40 mm (1.4–1.6 in) minimum internal |
| Height | 35 cm (14 in) for standard hydrometers |
| Base | Weighted or flat-bottomed for stability |
| Volume | 200–250 ml working volume |
Plastic is safer (won’t shatter), but glass is easier to sanitise and won’t scratch over time. A good test jar costs 5–10 EUR.
Sampling Thief (Wine Thief / Beer Thief)
A long tube used to pull samples from carboys and fermenters without opening the lid fully. Look for food-grade plastic or stainless steel, 45–60 cm (18–24 in) long.
Calibration: Your First Step with a New Hydrometer
Every hydrometer should be calibrated before its first use, and periodically thereafter (every 6–12 months).
Calibration Procedure
- Fill your test jar with distilled water (not tap water — dissolved minerals affect density).
- Bring the water to your hydrometer’s calibration temperature (check the label).
- Lower the hydrometer gently into the water.
- Spin it slightly to release air bubbles from the surface.
- Wait 30 seconds for it to stabilise.
- Read the bottom of the meniscus at eye level.
- It should read 1.000 (or 0.0 °Bx, or 0.0% potential alcohol on a triple-scale).
What If It Does Not Read 1.000?
| Reading | Meaning | Action |
|---|---|---|
| 1.001 | Reads 1 point high | Subtract 0.001 from all future readings |
| 0.999 | Reads 1 point low | Add 0.001 to all future readings |
| > ±0.002 | Out of acceptable tolerance | Replace the hydrometer |
Record your calibration offset and apply it consistently. A hydrometer that consistently reads 1 point high is still perfectly usable — you just need to account for it.
Why Calibration Drifts
Glass hydrometers are remarkably stable instruments. Calibration typically drifts only because of:
- Mineral deposits on the glass surface (soak in vinegar or PBW to remove).
- Scratches that trap liquid and change the effective buoyancy.
- Label shift — the paper scale inside the stem can slip if the seal degrades (rare in quality instruments, common in cheap ones).
Reading Techniques for Maximum Accuracy
The Meniscus Problem
Water climbs up the glass surface due to surface tension, forming a concave meniscus. Always read at the bottom of the curve, at eye level.
| Reading Position | Error Introduced |
|---|---|
| Top of meniscus | +0.001 to +0.003 (reads too high) |
| Bottom of meniscus at eye level | Correct |
| Below eye level (looking up) | Reads slightly high |
| Above eye level (looking down) | Reads slightly low |
Tip: Use a Flashlight
Hold a small flashlight or phone torch behind the test jar at the level of the liquid surface. This illuminates the meniscus and makes it much easier to identify the exact bottom of the curve.
Dealing with Bubbles
CO₂ bubbles clinging to the hydrometer artificially increase buoyancy, causing it to float higher (lower apparent gravity). In actively fermenting samples:
- Pour the sample vigorously between two containers 3–4 times.
- Let it rest for 60 seconds.
- Lower the hydrometer and spin it gently.
- Flick the top of the stem with your finger to release remaining bubbles.
- Read immediately — CO₂ will continue to come out of solution.
Hydrometer vs Refractometer: When to Use Which
| Factor | Hydrometer | Refractometer |
|---|---|---|
| Sample size needed | 100–200 ml | 2–3 drops |
| Accuracy pre-fermentation | ±0.001 SG | ±0.002 SG (with WCF) |
| Accuracy post-fermentation | ±0.001 SG | Requires correction — see Refractometer Post Fermentation Correction |
| Speed | 2 min (including temp) | 30 sec |
| Temperature sensitivity | High — needs correction | Moderate (ATC helps) |
| Durability | Fragile (glass) | Robust (metal/plastic housing) |
| Cost | 8–60 EUR | 25–80 EUR |
| Best for | FG readings, calibration, competition | Sparging, quick OG checks, brew day |
Most serious homebrewers own both. Use the refractometer on brew day for quick gravity checks during the mash and sparge (where you do not want to waste 200 ml of precious wort each time). Use the hydrometer for OG and FG readings where accuracy matters most.
For a full exploration of how to correctly use a refractometer — including the critical post-fermentation correction — see our Refractometer Post Fermentation Correction article. And once you have accurate readings from either instrument, our Abv Calculator Complete Guide will help you calculate ABV correctly.
Care and Maintenance
Storage
- Store vertically in the original tube or a padded case.
- Never store loose in a drawer where it can roll and break.
- Keep the test jar and hydrometer together so you always have both on hand.
Cleaning
- Rinse with warm water after each use.
- For stubborn residue: soak in PBW (Powdered Brewery Wash) for 30 minutes.
- Never use abrasive scrubbers — scratches affect readings.
- Sanitise before use if the sample will go back into the fermenter (though we recommend against this practice — always discard the sample).
What to Do When It Breaks
Glass hydrometers break. It is not a matter of “if” but “when.” Here is how to be prepared:
- Buy two — they are cheap, and having a spare means you never miss a reading on brew day.
- If it breaks into the fermenter: The liquid may be contaminated with glass shards and possibly lead shot. Discard the batch. This is the strongest argument for always using a test jar.
- Recycle the glass according to your local regulations. If lead shot was used as ballast, dispose of it as hazardous waste.
Summary: Recommended Buying Strategy
| Brewer Level | Recommendation | Estimated Cost |
|---|---|---|
| Beginner (extract kits) | 1 triple-scale + test jar | 12–18 EUR |
| Intermediate (all-grain) | 1 triple-scale + 1 precision (1.000–1.070) + test jar | 25–40 EUR |
| Advanced / competition | 2 precision hydrometers (1.000–1.070, 0.990–1.020) + thermohydrometer + refractometer | 80–150 EUR |
| Professional | NIST-certified precision set + digital density meter | 200+ EUR |
For most homebrewers, a single quality triple-scale hydrometer and a sturdy test jar are all you need to get accurate gravity readings and calculate ABV reliably.
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Methodology
Hydrometer accuracy specifications and calibration procedures in this article follow the guidelines established in OIML R 44 (International Recommendation for Hydrometers) and ASTM E100 (Standard Specification for ASTM Hydrometers). Calibration temperature standards (15.56 °C and 20 °C) are documented in the ASBC Methods of Analysis, Beer-2.
Product recommendations are based on hands-on testing, community reviews from HomeBrewTalk (homebrewtalk.com) and the BJCP Forum, and manufacturer specifications. Price ranges reflect European and North American retail prices as of early 2026 and may vary by region.
John Palmer’s How to Brew (4th Edition, Brewers Publications, 2017) was referenced for practical hydrometer usage guidance. The comparison of hydrometer vs refractometer performance draws on data from Sean Terrill’s refractometer experiments (seanterrill.com, 2011) and Dr. Michael Hall’s article “Brew by the Numbers” in Zymurgy (American Homebrewers Association, 1995). Meniscus reading error estimates are based on experimental data published in the Journal of the Institute of Brewing (Vol. 112, Issue 2, 2006).