In fact Merriam Webster [1] very explicitly advocates for "gauge":
> The verb gauge, which refers to measuring or estimating, also has a variant gage. This variant appears to show up primarily in informal sources, though not often. Gauge is by far the preferred spelling in general usage for both the noun and the verb; we encourage you use it.
> The verb gauge, which refers to measuring or estimating, also has a variant gage. This variant appears to show up primarily in informal sources, though not often. Gauge is by far the preferred spelling in general usage for both the noun and the verb; we encourage you use it.
1. https://www.merriam-webster.com/dictionary/gage