An unchanged hydrometer reading usually doesn't mean your batch is in trouble — it most commonly means you took the reading at a moment fermentation wasn't visibly active (either before it started or after it finished). The diagnostic below works out which scenario you're in.
"My hydrometer reading didn't change from yesterday" is a common moment of concern in homebrewing. The fix depends entirely on which of three scenarios you're in, and they need very different responses. This article walks through the diagnostic in order: figure out which scenario applies, then act accordingly.
What hydrometer readings should look like over time
For context, here's roughly what gravity progression looks like for a healthy 23-litre Pale Ale fermentation. Specific numbers vary by recipe, but the shape of the curve is consistent.
Two key observations from this. First: gravity drops most dramatically between days 2 and 7 — that's when you'd expect to see big changes. Second: by day 10-14, gravity has reached its final value and stays there. If you're taking readings at the front end (day 0-1) or back end (day 10+), the gravity may genuinely not change between readings, and that's normal.
The three scenarios
Match your situation to one of these three before deciding what to do.
What it looks like
You pitched yeast 12-48 hours ago. You took a reading shortly after pitching. You took another reading later that day or the next morning. Both readings are the same as your OG — the wort is still around 1.045-1.055.
Why it's happening
Yeast goes through a lag phase before active fermentation starts. During lag (typically 12-36 hours), the yeast rehydrates, absorbs oxygen, and multiplies before switching to consuming sugars and producing alcohol. During this phase, gravity barely changes.
What to do
Wait. Take another reading 48 hours after pitching, not 24. If your stick-on thermometer shows the wort is in the 18-20°C range, the yeast is fine — it just needs more time to start producing visible gravity changes. Most healthy fermentations show their first significant gravity drop between hours 36 and 72 after pitching.
What it looks like
You took a reading several days into fermentation, and it shows around 1.010-1.014. You came back 24-48 hours later, took another reading, and the number is the same.
Why it's happening
Fermentation completed faster than expected. Modern dry yeast strains pitched at the right rate on standard-gravity wort at the right temperature can complete fermentation in 5-7 days — not the 10-14 days most beginner guides quote. If your reading is in the normal final gravity range and stable across two readings, you're at the natural end of fermentation, not a problem.
What to do
Compare your current reading to the expected final gravity for your style. For a Hazy Pale Ale, that's 1.010-1.014. If you're in that range and the reading hasn't changed in 48 hours, fermentation is complete. Two more days of conditioning at fermentation temperature, then you're clear to bottle.
What it looks like
It's been 5+ days since pitching. Two hydrometer readings 48 hours apart show the same value. The reading is significantly above expected final gravity — for example, sitting at 1.025-1.035 when it should be at 1.010-1.014.
Why it's happening
Three main causes for genuine stuck fermentation: wort temperature dropped too low (yeast goes inactive below 16°C), yeast was under-pitched or weak (not enough viable cells), or yeast settled out of suspension early. The result is the same regardless of cause: fermentation stopped before all the fermentable sugars were consumed.
What to do
This is a real problem requiring intervention. The good news: most stuck fermentations recover with one of three actions — warming the wort, gently swirling to re-suspend yeast, or pitching fresh yeast. Our how to fix a stuck fermentation guide covers the full diagnostic and recovery sequence.
The quick decision tree
Working through which scenario applies, in order:
- How many days since pitching? If less than 48 hours: Scenario 1, wait.
- What gravity does the hydrometer show? If it's at or below the expected final gravity (1.010-1.014 for most Pale Ales) and stable across two readings 48 hours apart: Scenario 2, fermentation is done.
- If the gravity is significantly above expected FG and 5+ days have passed: Scenario 3, see the stuck fermentation guide.
For most homebrewers reading this article, Scenario 1 or 2 applies. Scenario 3 happens, but less often than first-time brewers fear.
Hydrometer readings don't change because (a) fermentation hasn't started yet, (b) it's already finished, or (c) it's genuinely stuck. Check the calendar and the gravity number against expected FG to know which one you have.
Make sure your hydrometer is reading accurately
Before assuming your gravity is genuinely stuck, sanity-check the instrument. A few things can cause inaccurate readings.
Sample temperature
Most hydrometers are calibrated at 20°C. If you took the reading on cold wort, the reading is artificially high; on warm wort, artificially low. The effect is small (1-2 points per 5°C of difference) but it matters at the precision level. Always let samples reach roughly 20°C before reading.
Bubbles on the hydrometer stem
Tiny CO2 bubbles attaching to the hydrometer can lift it artificially, giving a higher reading than reality. Spin the hydrometer gently in the test jar before reading to dislodge bubbles.
Sample drawn from the wrong part of the fermenter
The wort at the bottom of the fermenter is denser than the wort at the top (more yeast and sediment). Take samples through the fermenter tap, which draws from a consistent middle level, not from skimming the surface or stirring up the bottom.
Reading from the wrong meniscus position
The hydrometer reading should be taken at the surface of the liquid where it touches the stem — the bottom of the meniscus curve, not the top edge of the liquid film that climbs up. Reading from the wrong point can be off by 0.005 or more.
Most "stuck" readings turn out to be fine fermentation with bad measurement technique. Sanity-check the hydrometer before sanity-checking the beer.
When you can't take a reading at all
Worth flagging: don't skip readings just because the hydrometer is annoying to use. The hydrometer is the only reliable measure of fermentation progress — airlock activity, foam, and visual inspection are all indirect signals that can mislead.
If you don't trust your readings, take a small sample and use a fresh hydrometer at a controlled temperature, or buy a refractometer (which uses just a few drops of wort) for easier sampling. Going by airlock alone almost guarantees you'll either bottle too early or worry unnecessarily.
For broader fermentation diagnostics including the airlock side of the question, see our why is my homebrew not bubbling guide. If you've confirmed Scenario 3 and need to intervene, see how to fix a stuck fermentation. For the full brewing process this all builds on, see how to brew from a fresh wort kit.