Help me calculate a percentage contribution to a final total

December 8, 2010 10:55 AM

Excel help: I want to multiply two numbers, then subtract a percentage from that number, and arrive at a fourth number.

Here's what I want:

((A1 * A2) - A3) where A3 = a variable percentage, and arrive at a final number, A4.

In other words:

If 2 tickets (A1) cost $5 each (A2), and I agree to pay 70% (A3) of the total cost, then A4 = $3.

Everything I'm doing is ending up with a wonky number.

posted by Cool Papa Bell to Computers & Internet (6 answers total)

A4 = (A1 * A2) * A3

where A3 is expressed as a decimal value: in your example, 0.3.
posted by Tomorrowful at 10:57 AM on December 8, 2010

((A1*A2) - (1-A3)*(A1*A2)
posted by inigo2 at 10:58 AM on December 8, 2010

Response by poster: Can I get it so I don't have to set it a decimal value? I want someone to just enter "70" if they want to contribute 70 percent.
posted by Cool Papa Bell at 10:58 AM on December 8, 2010

Best answer: If A1 is the number of tickets, and A2 is the cost of a single ticket, and A3 is the percentage you agree to pay, then the formula in A4 should be

=(A1*A2)*(A3/100)
posted by mbd1mbd1 at 10:58 AM on December 8, 2010 [1 favorite]

Response by poster: Bingo.

I have no idea why that was so hard for me. Thanks!
posted by Cool Papa Bell at 11:01 AM on December 8, 2010

You say "bingo", but in fact mbd1mbd1's formula produces the amount that you pay, while your original question asked that A4 yield the amount that the other party needs to pay. If that's still what you want, then given the terms you laid out in the original question, the formula needs to be

=(A1*A2) * (1-(A3/100))
posted by muhonnin at 12:18 PM on December 8, 2010