The percentage on a chocolate wrapper tells you less than it appears to

What the number actually counts

The figure on a dark chocolate wrapper is the proportion of the bar, by weight, derived from the cocoa bean. That includes the cocoa solids, which carry essentially all of the colour and most of the flavour, and the cocoa butter, which carries almost none of either and is responsible for the melt. The two are counted together, and the label doesn’t tell you how they are split.

This isn’t a small omission. A seventy percent bar might be made of fifty parts cocoa mass and twenty parts added cocoa butter, or of sixty-five parts mass and five parts butter, and those are noticeably different products. The first is softer, milder and richer in the mouth; the second is more intense, drier and firmer. Both are honestly labelled seventy percent.

The rest is almost always sugar

Whatever is not cocoa in a dark chocolate is sugar, give or take a fraction of a percent of lecithin and any vanilla. So a seventy percent bar is thirty percent sugar and an eighty-five is fifteen, and reading the number as a sweetness scale in reverse is the one thing it genuinely does reliably. That is why the figure caught on: it is a proxy for sweetness that happens to be easy to print.

Milk chocolate complicates it immediately, because milk solids and milk fat occupy part of the bar and the cocoa percentage now shares the remainder with both sugar and dairy. A milk chocolate at forty percent may be a serious piece of work or a very ordinary one depending on how much of the rest is milk and how much is sugar. The percentage alone cannot distinguish them, and the ingredient list, which is ordered by weight, usually can.

Why higher percentages behave differently in a recipe

Substituting an eighty-five percent bar into a ganache written for a fifty-five changes three things at once. There is less sugar, so it tastes far more bitter and the balance of the whole preparation shifts. There are more cocoa solids, and those solids absorb liquid and thicken, so the emulsion becomes stiffer and more prone to splitting. And the fat proportion is usually different, which changes the ratio the ganache was calculated on.

This is why ganache recipes specify a percentage and mean it, and why the ratio of cream to chocolate is quoted differently for dark, milk and white. The conventional adjustment is to use less liquid for a lower-percentage chocolate and more for a higher one, which sounds backwards until you remember that it is the dry cocoa solids doing the thickening rather than the fat.

Percentage is not quality and does not track it

A high figure guarantees only that a large fraction of the bar came from a bean. It says nothing about which beans, how they were fermented, how they were roasted, how long they were conched or whether they were any good. A poorly fermented cocoa at ninety percent is a punishing thing to eat, and a well-made bar at sixty can be far more complex.

There is also a floor below which the word dark stops meaning much, since a bar can be more than half sugar and still avoid being called milk chocolate simply by containing no dairy. The percentage is at its most useful at that end of the range, where it separates a genuinely dark bar from a sweet one wearing the same word on the front.

The market has drifted upward regardless, partly because a high number reads as serious and partly because it correlates loosely with the small-batch makers who do care about all the earlier stages. The correlation is real and the causation is not. Tasting remains the only method, which is an unsatisfying conclusion and an accurate one.

A few things the number does predict

Setting behaviour is one. More cocoa butter means a firmer snap and a cleaner set, and a very high-percentage bar with little added butter can be brittle and awkward to work with because there is proportionally less fat to carry the solids. Viscosity when melted is another, and it moves in the direction people find surprising: high-cocoa bars are often thicker to work with, because the solids are what resist flow.

Shelf life is a third. Sugar and fat both discourage spoilage, water content is negligible in all of them, and dark chocolate keeps longer than milk largely because milk solids bring their own vulnerabilities. None of these has much to do with how the bar tastes, which is the thing the number is most often used to argue about.