The Research & Development to Sales ratio is a measure to compare the effectiveness of R&D expenditures between companies in the same industry. It is calculated as R&D expenditure divided by Total Sales. This is measured on a TTM basis.
This is calculated by dividing the Research & Development Expense by total sales or revenue.
R&D expense is not always broken out in a company's financials, however, so this value may be n/a in those cases.
Comparisons are not always useful across industries - for example, pharmaceuticals and software companies tend to spend a lot on R&D while consumer product companies spent less.
This is measured on a TTM basis.