How to use this calculator
Choose whether you know the shooting window or want a particular clip length. Enter an interval measured from the start of one exposure to the start of the next and the playback frame rate. Target mode rounds up to enough whole frames to meet the requested clip length, then shows a planned shooting window and the actual clip duration. Open Exposure and still-photo storage to check your exposure and average saved image size. Exposure must be shorter than the interval.
The formula
A worked example
A 60 minute window at a 10 second interval contains 360 frame starts, from 0 to 3,590 seconds. At 24 fps, the clip is 15 seconds; saving 25 MB stills needs about 9 GB. For a target 10 second clip at 24 fps and a 5 second interval, plan 240 frames across a 20 minute window. With 0.5 second exposures, the last starts at 1,195 seconds and ends at 1,195.5 seconds. A 10.01 second target instead needs 241 frames and produces about 10.0417 seconds of playback.
Assumptions & limitations
Uses first-frame-at-zero and an end-exclusive window; camera implementations can differ. Target mode plans one full interval per frame, not the minimum elapsed capture time: the last exposure ends earlier, as shown. In shooting-window mode, the last exposure may end after the entered window because frames are counted by start time. Exposure shorter than interval does not guarantee enough processing or write time; missed frames shorten the clip. Photo storage applies only when saving separate stills, such as RAW or JPEG sequences. In-camera movie modes may save only a movie, whose size is not estimated here. No start delay, camera-specific limits, file overhead or storage reserve is added.
Common questions
Why can a tiny timing change add one frame?
The first frame starts at zero, and a start exactly at the window end is excluded. A start even slightly before the end counts. Displayed times are rounded, so two displayed times can look equal while the stored values differ. Use the worksheet’s full-precision record to inspect them.
Does the interval include the exposure?
Yes. It is start-to-start. Leave time after each exposure for processing, writing, and camera behavior.
Why is the last exposure earlier than the planned shooting window?
Target mode reserves one full interval per frame. The first exposure starts at zero, so 240 frames at a 5 second interval start from 0 to 1,195 seconds within the 1,200 second window. The final exposure can finish before the window ends.
Why might the finished clip be longer than my target?
You can capture only whole frames. The target frame count rounds up, so the planned clip meets or slightly exceeds the requested length at the playback rate you entered.
Does photo storage estimate the finished movie size?
No. It estimates separately saved still photos. Some in-camera time-lapse modes save a movie without retaining individual photos. Check your camera manual; encoded movie size depends on its bitrate and format.
Why might my camera count a different number?
Some cameras include a frame at the ending time or round the number of intervals differently. A camera may also skip shots if exposure, processing, focusing or card writing takes too long. Check your camera’s convention and test the chosen settings.
Supporting reference
The method above states this calculator’s assumptions. This reference provides related definitions and technical context.
Nikon: D850 time-lapse movie planning ↗Formula and worked example checked against automated test cases. About our methodology.