Co. is raising $1.7 million
Offering 35% of its common for this amount.

what is the pre-money valuation?
what is the post-money valuation?

Please show calculation

Hi...I'm just a user here, but I am a venture capitalist and
investmetn banker, so I can help.  I notice there is no answer right
now, so perhaps I can give you some info.

Pre-money valuation is the value of the company before adding the new
investment; post money is the value of the company after the
investment.

So, if you purchase 35% of the company for $1.7 million, the PRE-Money
valuation is $1,700,000/.35, less $1.700,000, or $3,157,000.

The POST-money value is the $4,857,000, which equals the pre-money
($3,157,000) plus the investment ($1,700,000 cash invested).

This makes sence because, immediately, the investor has the same value
he or she put in: 35% of $4,857,000 is $1,700,000.

An easier way to look at it is to consider simple numbers and a very
simple "business."

Say you have a "business" which is basically, $1,000,000 sitting in a
bank account.  Your pre-money valuation is clearly $1,000,000.  If you
go to an investor, and want to sell half the company, you would ask
him to put in an additional $1,000,000 for 50% of the company.  The
post-money value is $2,000,000 (the pre-money value ($1,000,000) plus
the $1,000,000 investment).

Again, it makes sense: the investor put in $1,000,000, and now owns
50% of $2,000,000, and the founder still has the exact same amount of
equity (the other $1,000,000).

The idea, of course, is that the investment will add value to the
whole, and the returns will benefit all shareholders.

Good luck.