When writing ranges of numbers, most style guides agree on the use of an en dash (although the AP style guide prefers a hyphen). Do not use an em dash.

En dashes, which are about the width of an upper-case N, are often mistaken for hyphens. But, traditionally, en dashes function as a kind of super hyphen. They’re meant to give you a little extra glue when you have a compound modifier that includes a multi-word element that can’t easily be hyphenated. For example, the phrase Elvis Presley–style dance moves uses an en dash because Elvis-Presley-style dance moves is awkward; “Elvis Presley” isn’t a compound modifier, so hyphenating it looks odd. But, keep in mind, not all readers will notice en dashes or understand what they mean. Sometimes, it’s better to simply reword the phrase. Elvis Presley–style dance moves or: dance moves like Elvis Presley’s pre–World War II buildings or: buildings constructed before World War II En dashes are also used to show ranges of numbers, such as times, page numbers, or scores (I’ll schedule you from 4:30–5:00). But, outside of formal printed publications, this type of en dash is commonly replaced with a simple hyphen.

Use it betweenwords that indicate a duration, such as hourly time or months or years. Useit where you would otherwise use the word “to.”