How Big Is Big?

When numbers are meaningless

It’s that time of year again. Wildfires are starting to spread, well, like wildfires. And meaningless measurements of the size of those fires are spreading, too.

“So far this year, 261 fires have burned about 260,000 acres statewide,” one report said. “Last year during the same period, 193 fires had burned less than 10,000 acres.”

“Crews have finished replanting about 900 acres in northern Arizona’s Kaibab National Forest that were burned during a 2006 fire,” said another report. “Some 1,600 acres were replanted in 2008, bringing the total to 2,500 acres replanted in the restoration project.”

Can you visualize any relationship between the size of these fires or replanting and something you recognize? Probably not.

One reason “acres” are used to measure the size of forest and brush fires is that land is generally measured in “acres,” and those fires occur on land. But not many people whose job doesn’t involve the land can tell you how big an “acre” is.

We can. An acre is 43,560 square feet.

That doesn’t help much, does it? It’s too hard to imagine that many square feet.

How’s this? An acre is about three-quarters the size of a football field (including the end zones).

That should help. If you have a one-acre fire, it’s easy for a reader to visualize its size. But that 260,000-acre figure above translates to the equivalent of about 3,500 football fields. Hard to visualize again.

So what’s a better measurement? Square miles are useful. (A square mile is 640 acres.)* Nearly everyone knows how long a mile is, and it’s easier to visualize the size of a square with one mile on each side.

Using square miles also makes the numbers seem less dramatic. The 2,500 acres that were replanted in Arizona in the example above translates to about four square miles, which suddenly doesn’t seem so big. The 260,000-acre figure above is about 406 square miles. Putting them in a more manageable perspective will allow readers to say “Gee, that’s big.” Or not.

But you should be cautious with square miles, too: Just how big is 406 square miles?

American readers can usually understand the timeworn—but effective—comparison to the size of a state. For example, 406 square miles is about a quarter of the size of Rhode Island (1,545 square miles), or the equivalent of six Districts of Columbia (68.25 square miles). Or you can use a local equivalent: In the Southwest, you can say that the 260,000 acres consumed by fire is the equivalent of about one-quarter the size of Grand Canyon National Park; in the Northeast, it could be equivalent to almost eighteen Manhattans. The point is to keep the “equivalent” number small and relevant.

One further caution: Use “equivalent” when giving a size or comparison. No fire consumes in a rectangular pattern, so even “square miles” or “acres” can make a reader think of a nice, neat pattern. And fires are nothing if not messy.

Making better comparisons can make for fewer “acres” and pains for readers.

Correction: This article originally reported that a square mile is about 640 acres. In fact, it is exactly 640 acres. CJR regrets the error. Return to the corrected sentence.

Has America ever needed a media watchdog more than now? Help us by joining CJR today.

Merrill Perlman managed copy desks across the newsroom at The New York Times, where she worked for 25 years. Follow her on Twitter at @meperl.