CURDCRAFT

pH & Acidity Calculator

Turn a titration reading into % titratable acidity and Dornic degrees, and see the typical target range for the stage of the make you’re at.

The volume of titrant it took to reach the phenolphthalein endpoint.
Standard titration uses 0.1 N sodium hydroxide.
The classic method titrates a 9 mL sample.

Titratable acidity

% lactic acid (TA)
0.15%
Dornic degrees
15° D

Typical target — Fresh milk

TA% range
0.13–0.17%
pH range
6.6–6.8

Acidity is the clock your whole make runs on

Every stage of a cheese make — ripening the milk, renneting, cutting the curd, draining, and salting — is timed around a target acidity, not just a clock on the wall. Two batches started at the same time can reach the same acidity minutes or hours apart depending on the culture, the milk, and the room temperature, which is exactly why experienced cheesemakers test acidity directly instead of only watching the timer.

Titration is the traditional, equipment-light way to do that testing, and it's still what most small-batch recipes assume you're using when they specify a target %TA or °D at a given step.

Frequently Asked Questions

What is titratable acidity, and how is it different from pH?

Titratable acidity (TA) measures the total amount of acid in the milk by neutralizing it with a base (sodium hydroxide) — it tracks how much lactic acid the culture has produced. pH measures the concentration of free hydrogen ions instead. The two are related but not identical, and TA is what the classic titration test in this calculator actually measures.

How do I actually run the titration at home?

Add a few drops of phenolphthalein indicator to a small milk sample (traditionally 9 mL), then add standardized 0.1 N sodium hydroxide drop by drop from a syringe or burette while stirring, until the sample just turns a faint, stable pink. The volume of NaOH used is your titrant reading for this calculator.

What are Dornic degrees?

Degrees Dornic (°D) are an older European scale for milk acidity, still printed on some culture and dairy-supply instructions. One Dornic degree equals 0.01% lactic acid, so the conversion is simple: multiply your % titratable acidity by 100 to get degrees Dornic.

My acidity is climbing faster or slower than the target range — what's going on?

Culture activity is very temperature-sensitive, so a vat that's a few degrees warmer or cooler than intended will acidify faster or slower than expected. An old or weak culture, a prior antibiotic residue in the milk, or simply not enough ripening time can also leave a batch under-acidified at renneting.

Educational estimate only, based on the standard titration formula. Lab technique, indicator freshness, and equipment all affect the real reading — treat the target ranges as typical guidance, not a guarantee.