ROASとは、広告の費用対効果を現す指標のひとつで、広告費用に対して得られた売上金額の割合を意味します。売上金額を出稿した広告費用で割ることで算出できます。
「広告出稿によって、どのくらい売上が伸びたのか」を示すことができ、ROASが100%以下であれば、その広告キャンペーンにかけた広告費用は売上よりも高かったことを意味します。単一の商品・サービスだけを扱っている場合は、数式上は商品・サービス単価をCPA（Cost Per Acquisition）で割ることでROASを算出できます。100%に満たない場合は売上が広告費用を下回っていることになります。
ROAS（%）＝売上÷広告費×100
ROAS (Return On Advertising Spend)
ROAS is one of the indicators that shows the cost effectiveness of advertising, and it means the ratio of sales amount obtained to advertising cost. It can be calculated by dividing the sales amount by the advertising cost.
It can show how much sales have increased due to advertising, and if ROAS is less than 100%, it means that the advertising costs spent on that advertising campaign were higher than sales. If you only deal with a single product or service, you can calculate ROAS by mathematically dividing the unit price of the product or service by the CPA (Cost Per Acquisition). If it is less than 100%, sales are less than advertising costs.
ROAS (%) = Sales ÷ Advertising expenses x 100