Intervalometer Shot Count Calculator
An intervalometer fires the shutter at a fixed interval over a session, so before you head out it helps to know how many frames you will capture and how much card space they need. This calculator returns the shot count and the total storage required from your session duration, the interval between shots, and the average file size. Use it to size a memory card, plan a time-lapse, or check a long-exposure sequence will fit.
Intervalometer formula
Shots = floor( session seconds / interval ) + 1
Storage MB = shots * file size MB
Storage GB = storage MB / 1,024
The plus one accounts for the first frame at time zero. Storage divides by 1,024 to convert megabytes to gibibytes, the binary gigabyte cards are sold in.
Worked example
A 120 minute session (7,200 seconds) at a 10 second interval with 25 MB files: shots = floor(7,200 / 10) + 1 = 720 + 1 = 721. Storage = 721 * 25 = 18,025 MB = 18,025 / 1,024 = 17.60 GB. A 32 GB card has ample room.
Intervalometer: frequently asked questions
How many shots will my intervalometer take?
The shot count is the total session time divided by the interval, plus one for the first frame at time zero. A 2 hour session at a 10 second interval gives 7,200 / 10 + 1 = 721 shots.
How much storage do I need for an interval session?
Multiply the number of shots by the average file size. At 721 shots and 25 MB per RAW file, you need about 18 GB of card space. Always allow headroom because file size varies with scene detail.
Should I add one to the shot count?
Yes. The first frame fires at the start (time zero) and then one frame per interval after that, so the count is duration divided by interval, rounded down, plus one. This calculator includes that opening frame.
Sources
- NIST: Time and Frequency Division (the second).
- Shot count and storage use only the definitions of interval, duration, and file size; no external figure is required.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.