ROAS, ACOS and TACOS in one minute
ROAS is revenue per dollar of ad spend. ACOS is ad spend as a share of ad revenue, so it is 100 divided by ROAS. TACOS compares ad spend with all your sales, not only the ones ads produced. Amazon sellers usually watch ACOS and TACOS. Shopify, Google and Meta advertisers usually watch ROAS.
From measuring to deciding
The first calculator tells you what your ads are returning. The second tells you what they need to return. Compare the two: if your actual ROAS is above the break-even ROAS you make money on the ad sale, and if it is below you lose money on it. To improve the result without spending more, look at your conversion rate with the CRO calculators.