The largest mass extinction in history was not as severe as previously suspected, a University of Hawaii scientist has calculated.

But it was still pretty bad.

The so-called Permian extinction 250 million years ago eliminated 81 percent of species in the ocean, estimates Steven Stanley, a paleontologist at the UH School of Ocean and Earth Science and Technology.

A scientific publication in 1979 mistakenly lumped together two mass extinctions and concluded that between 88 percent and 96 percent of marine species died out at the end of the Permian. That led to widespread claims that life nearly ended at the end of that period.

“About 90 orders and more than 220 families of marine (species) persisted into the Mesozoic Era, the ‘Age of Dinosaurs,’ and they embodied an enormous amount of morphological, physiological and ecological diversity,” Stanley said in a news release.

“Many of those species went on to diversify substantially. Life did not nearly disappear at the end of the Permian, as has often been claimed.”

Stanley’s findings are in the latest issue of Proceedings of the National Academy of Sciences.

Stanley came up with a way to estimate and subtract the magnitude of background extinctions — those that had nothing to do with the mass die-off.

About 70 percent of terrestrial species died out, scientists estimate.

Possible causes range from an asteroid impact to volcanism to runaway climate change from the release of methane from the seafloor.