If so, any thoughts on how to determine approximately how much lighter

You can find out exactly how much lighter.

There's nothing about a formula that defines or describes color appearance.

Because it's just a list of ingredients.

The psychophysical sensations of hue/color, lightness, and chroma can't be derived from the formula.

Just like you can't read the list of ingredients on the back of a cake mix and know how it's going to taste.

Have to measure the colors.

It's easy.

Store should be able to do it for you or you can do it yourself.

Either way, need to carefully paint small samples. One full coat let it dry. Second coat let it dry.

Order a Color Muse from Amazon

Download Color Muse app

Change settings to D65 Illuminant, 2° Observer

Choose "Compare" in lower left corner

Hit the 3 dots in upper right corner > Switch to Advance Mode

Scan Color 1 > Scan Color 2

Compare L = Lightness. Bigger number is the lighter color

Thanks, Lori. I was hoping there was an easy conversion chart where I could plug in the numbers. Given all the research I’ve done, I should have known it wasn’t so simple. I have compared samples, but it’s still not the same as having the entire room painted. Appreciate the feedback.