Sourdough Starter Not Doubling? Here’s What Actually Matters (and a Better Way to Measure Strength)

If your sourdough starter isn’t doubling in size, it’s very easy to assume something is wrong. But here’s the truth: doubling is one of the most misunderstood “tests” of starter strength, and it can be influenced by a dozen variables that have nothing to do with whether your starter is healthy.

In this guide, I’ll show you what matters more than doubling, how to check your starter at the right time (this is the big one), and a simple way to measure strength that works in real life.

Why “Doubling” Can Be Misleading

Rise is affected by more than just fermentation. Two starters can be equally active, yet rise very differently depending on:

• Hydration (consistency): A runny starter lets gas escape, so it won’t “hold” a big rise.
• Flour choice: Wholemeal/rye ferments quickly but can rise differently due to structure.
• Jar shape: A wide jar makes the same rise look smaller than a tall narrow jar.
• Timing: If you check after it has peaked and fallen, it will look flat (even if it was strong earlier).
• Temperature: Warm kitchens peak fast; cool kitchens peak slowly and may never “balloon”.

So the real question isn’t “did it double?” — it’s did it ferment well, and did I catch it at its peak?

The Rise + Fall Cycle (This Changes Everything)

A sourdough starter doesn’t just rise forever. It follows a cycle:

1. Feed (fresh flour + water)
2. Rise (gas builds and the starter expands)
3. Peak (maximum height + activity)
4. Fall (it deflates as food runs low and structure weakens)

Here’s the key: photos after 24 hours are often useless. In many conditions, especially warm weather, a starter can peak at 6–8 hours and be back down by 24 hours. So it looks like “it didn’t rise” when it actually did — you just missed the peak.

A Better Way to Measure Starter Strength

Instead of obsessing over doubling, look for these reliable signs:

• Predictable timing: It rises and peaks consistently after feeds (even if the rise is modest).
• Visible fermentation: Bubbles throughout (not just a few on top).
• Texture change: It becomes lighter, aerated, and “mousse-like” at peak.
• Smell: Pleasantly sour, fruity, yeasty (not harsh solvent/rotting).
• Peak markers: A domed top at peak, then a slight concave top when it starts falling.

If these are present, your starter is doing its job.

Jar Markings: The Simple Trick That Stops the Guessing

This is the easiest upgrade you can make: mark your jar.

1. After feeding, scrape the sides down.
2. Use a rubber band or marker line to mark the level.
3. Check every couple of hours until you learn its normal peak time.

Once you do this, you’ll stop wondering if it “rose” — you’ll be able to see exactly how far and when.

Consistency (Hydration) Matters More Than You Think

If your starter is too thin, it can ferment strongly but still look flat. Why? Gas escapes instead of being trapped.

As a rule of thumb, a healthy starter at peak should feel thick enough to hold bubbles — not pour like pancake batter. If you’re consistently seeing low rise but lots of bubbles and acidity, try slightly lowering hydration (a thicker mix) and see if it holds structure better.

Feed Ratios That Work (Including 1:3:3)

A great “all-rounder” feed ratio for strengthening is 1:3:3 (starter : water : flour by weight).

• Why it works: It gives the starter more food, helps it build strength, and reduces the chance it becomes overly acidic and sluggish.
• When to use it: If your starter smells sharp/sour quickly, peaks early, or seems hungry before you can use it.

Example: 20g starter + 60g water + 60g flour.

Tip: Don’t wait a full 24 hours out of habit. If your starter peaks earlier (common in warm weather), you can feed it again at peak or shortly after it starts to fall.

Temperature: Why Your Starter Acts “Different” Week to Week

Temperature is the hidden driver behind most sourdough confusion.

• Warm conditions: Faster rise, earlier peak, quicker fall. You can easily miss the peak.
• Cool conditions: Slower rise, later peak, often denser texture and less dramatic expansion.

So if your starter “was doubling last week but not this week”, it’s often just temperature — not a dying culture.

Flour Choice: What to Expect

Different flours behave differently, and that’s normal:

• White bread flour: Often gives the most reliable rise and structure.
• Wholemeal: Ferments quickly, can be very active, but rise can vary due to bran cutting structure.
• Rye: Very fast fermentation and strong aroma; often looks “pasty” and doesn’t always rise like white flour starters.

If you’re troubleshooting rise, try feeding with bread flour for a few feeds and see if the structure improves.

Final Thoughts

If your starter isn’t doubling, it doesn’t mean it’s failing. What matters is predictable peaking, visible fermentation, and timing — and the easiest way to confirm that is to mark your jar and observe it around the 6–8 hour window after feeding.

Once you stop judging a starter by one single metric, sourdough becomes far more consistent (and far less stressful).

Helpful links: Sourdough Baking Guide | Sourdough FAQ

Shop sourdough essentials: Sourdough Starters | Sourdough Tools