ROI calculator

What to know

The ROI page asks for two amounts, Cost and Sale or final value, and returns a percentage. The formula is ROI = (final - cost) / cost x 100, with the net change (final minus cost) and the cost shown on the lines beneath.

Worked example: cost 1,000,000 and final value 1,500,000 gives (1,500,000 - 1,000,000) / 1,000,000 x 100 = 50 percent, a net change of 500,000. A final value of 800,000 gives -20 percent, so a loss shows as a negative number with a negative net change.

Cost must be greater than zero, because the formula divides by it, and both amounts must be zero or positive and no larger than 999,999,999,999. The result is not annualised, so a 50 percent return over six months and over five years read the same.

To compare investments of different lengths, divide by the years yourself or use the compound-interest page for an annual-rate view. Fees, taxes and dividends are not included unless you fold them into the two amounts.

A 25 percent gain is cancelled by a 20 percent loss, not by 25, which is why the percentage alone does not show symmetric ups and downs. ROI cannot fall below -100 percent, because a final value of zero already means the entire cost is lost.