The Knot (http://www.theknot.com) reports that there are many factors that go into deciding how much money to gift to a bride and groom. It is recommended to come up with a sum of money that you intend to spend on all gifts for the couple, based on your own finances and your relationship to the couple. It's generally expected that you spend more money the closer you are to the couple. Next, allot 20% of that total to the engagement present, 20% to the shower gift, and 60% to the wedding gift. Or, you can use the handy calculator at http://www.theweddingenvelope.com/calculator.php
The amount you’ll give to the bride and groom depends on your finances. If you have a lot of money then u can give generously to the couple. If your finances aren’t that stable, you can give the couple liberal amount based on the average norms of your customs in wedding.
Give an amount that you can afford and that you are comfortable with. The average amount of a wedding gift varies considerably. The popular wedding site www.theknot.com suggests that if you’re a co-worker or a distant friend or relative, $50 to $75 is a proper amount. If you’re a very close friend or relative, give $100 to $150. If you consider yourself anything in between, try for the $75 to $100 range. If you’re still worried, ask someone you know for feedback.