LONDON, April 10 — Should it be slithery or scrunchy, glutinous or grilled? The answer, British scientists say, may be divined by a formula: N = C + {f b (c m ) · f b (t c )} + f b (T s ) + f c · t a .

That is the scientific answer to the question: what makes the perfect bacon sandwich?

And, no, it is not April 1.

Researchers at Leeds University spent more than 1,000 hours testing 700 variants on the traditional bacon sandwich, which many Britons refer to as a bacon butty (eschewing the term sandwich, said to have been coined to honor the fourth Earl of Sandwich’s habit of eating meat between slices of bread around 1762).

For Britons, butties come in a variety of guises — chip butties (French fries between slices of bread), crisp butties (ditto with potato chips) or even sugar butties, which are self-explanatory. None are viewed as especially healthful.