On average you are going to need approx. 40MB per minute for HD video (1080p). So a 10 minute video will consume almost 400MB. If you use the Pause/Resume feature, you won't use nearly as much space, but keep an eye on the recording time so you'll be able to gauge.
TIP: If you have an iPhone 7 or better you can save 1/2 the space by selecting the video Custom Settings option and using the "High Efficiency" option.Tags: features, saving, videos