FishRuler Support
Everything you need to get accurate measurements with FishRuler. If your question isn't answered below, we're one email away.
How to measure a fish
Open FishRuler
Launch the app and allow camera access on first run. The AR view starts immediately.
Point at your fish
Lay the fish on a flat surface and hold your iPhone roughly above it, so the whole fish is in view.
Tap the head
Tap the tip of the fish's snout on screen. A marker is pinned to that spot in 3D space.
Tap the tail
Tap the end of the tail fin. The length appears instantly in centimetres.
Fine-tune if needed
Drag either marker to adjust. The measurement updates live as you move it.
Reset for the next fish
Tap Reset and you're ready for the next catch — no other steps needed.
Frequently asked questions
Which iPhone models are supported?
FishRuler needs the LiDAR scanner, which is built into iPhone Pro and Pro Max models from iPhone 12 Pro onwards (and iPad Pro models with LiDAR). Non-Pro iPhones do not have LiDAR and are not supported.
How accurate is the measurement?
Under good conditions accuracy is typically within about ±1 cm. For best results, lay the fish flat, hold the iPhone directly above it at 30–60 cm distance, and make sure the scene is reasonably lit.
Does it work without an internet connection?
Yes. LiDAR and AR processing run entirely on the device, so FishRuler works at remote beaches, offshore and anywhere without signal.
Which units are used?
Lengths are shown in centimetres with 0.1 cm resolution.
Does the fish have to lie flat?
You get the best accuracy with the fish lying flat on a board or the ground. Measure the straight line from snout tip to tail end, which matches how legal sizes are defined.
Does FishRuler collect any data?
No. The app has no account, no analytics and no ads. Camera frames are processed on your iPhone only — nothing is uploaded anywhere. See the Privacy Policy for details.
Still need help?
Send us an email and we'll get back to you as soon as we can — usually within a couple of business days.
Email support