If you are talking about the bid ROI, it is a combination of the estimated SBD and STEEM POWER to be received due the vote value, after curation (75%) and converted to USD, divided by the total amount (STEEM or SBD) of the bid sent by the user, also converted to USD. To have at least 1% the result of this division must be at lease 1.01. It is important to note that all this calculation is an estimation at the time of the bid, because the effective reward depends on the price of the STEEM and SBD at the moment of the payout (after the post reaches 7 days old).