base sth off of sth - отталкиваться (в расчетах, оценках и т. п.) от чего-либо

Until that time, we will continue to base our valuation off of our FY03 EPS estimate, which at a 12.5x multiple provides us with a price target of $24.
http://www.jagnotes.com/archive_jagnotes_body.cfm?jagdate=05...
(а до тех пор при определении цены мы по-прежнему будем отталкиваться от...)

Second, how does changing the overtime pay structure to cut out working professionals from being entitled to overtime help the economy? In my opinion we should entitle everyone to overtime pay, not base it off of income levels.
http://www.congress.org/congressorg/bio/userletter/?letter_i...

In the case of a one liter bottle, it will be about 27 cm long, but you should not measure it. Just base it off of the bottle itself.
mathforum.org/models/surface.html

This presents difficulties because the only method we can think of to estimate how many subscribers we'd have if we were monthly is to base it off of the rule of thumb that says that the players online represent 15% of your total player base (this estimation given by the $10/month people).
http://www.kanga.nu/archives/MUD-Dev-L/2001Q2/msg00903.php

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Note added at 2003-10-02 13:33:18 (GMT)
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или: \"основываться на\",
но \"отталкиваться\" может лучше подойти в Вашем контексте, т. к. это выражение часто передает неуверенность, приблизительность, когда такие расчеты делаются за неимением более точных данных (как это видно из ссылок выше).