Units To lays out frequency units one to a row and amounts one to a column. Opened at hummingbirds’ wings, it reads any amount of them at once in hertz, revolutions per minute, kilohertz, millihertz, beats per minute and every other frequency unit, even heartbeats and concert as. Type an amount the way you would say it, lay out a range of amounts, and choose how many decimal places to show.