$225,000 in Boston ≈ €361,633 in Paris

$225,000 in Boston requires €361,633 in Paris to match on household net cash. The gap is real, but it is smaller than the nominal numbers suggest once taxes run their course. Progressive brackets compress the after-tax difference faster than a compensation benchmarking site would lead you to believe, because those sites show gross and stop there.

The effective tax rate goes from 27.0% in Boston to 62.7% in Paris. That 35.7-point jump is what the equivalence solver is working against when it finds the matching gross salary.

Unvested equity changes this calculation entirely. RSU value is not modeled in the defaults above, but if you are mid-cycle at your current employer, leaving means forfeiting grants you have already been working toward, and that difference can be larger than the annual take-home delta that drove the comparison in the first place. The Advanced section's "RSU / stock annual value" field is where you plug that number in. Equity-heavy comp favors lower-tax cities at vesting; the after-tax discount gets larger the bigger the grant.

On an employer plan the healthy years feel nearly free; it's the bad year that finds the gap. Paris is universal, so most of that tail risk goes away. Boston still runs $4,100 a year in premiums and out-of-pocket costs, and none of it shows up on an offer letter.

Paris engineers get 25 vacation days per year. Boston averages 15. That 10-day gap is real money at a senior IC's daily rate, and it does not show up on the offer letter.

No kids, employer healthcare, and a single high-bracket income: this is the configuration that makes Boston look best in a head-to-head comparison. It is also the configuration most likely to change. The family scenario page (linked below) models what shifts once childcare and a second earner enter the picture.