A reasonably accurate way to check exposure, in my experience is to start with a gray card if you have one or with a piece of white paper for which you know the reflectance (see the package it came in). If you use a gray card, determine in advance if it's 18% or 12% reflectance (or whatever)

Then, on a clear day in the mid-latitudes at mid-day, carefully take some test photos of the target. I know not everyone is in the mid-latitudes but life isn't perfect.

Why those test conditions? Because the EV should be close to 14.7 (Sunny 16 "rule").

Now view the image file in any of many available viewers or editors that can show a histogram. But, in my experience, the raw image histogram shows a lower exposure (left of center) as compared to the JPG. Be aware that there is no applicable standard for raw, only for JPG.

If you used a white target you need to compensate for the difference in reflectance (example: 92% vs 18%).

This is not really perfect and you have to take care to take your test exposure without angles that distort the reading. Since most cameras show "live" exposure, you can wiggle the target to know in advance how you are doing.

This is "old school" stuff but it's still correct.

With those test conditions you can compare your camera's or meter's readings to what you know they should be and you can also check the results on your computer.