How to make UI pixels the same size as other asset pixels?

If you mix SpriteRenderers with CanvasRenderers you need to keep them in sync size-wise.

If you keep the SpriteRenderers fixed (sounds like you have decided already?) then the tweaking will likely be done via the CanvasScaler.

Here’s more reading:

Here are the official docs on how to make your UI handle various resolutions and aspect ratios cleanly:

Here are some notes on UI Anchoring, Scaling, CanvasScaler, etc:

Usually you need to choose a suitable ScaleMode and MatchMode in the Canvas Scaler and stick with it 100%. Generally if you change those settings you will often need to redo your UI entirely.

I also use this CanvasScalerOrientationDriver utility to make sharing UI for Landscape / Portrait easier. Read what it does carefully.