What is a post-money valuation?
The post-money valuation is the company's agreed value immediately after an investment: pre-money valuation plus the new money. Investor ownership is simply investment divided by post-money — a $5M check at a $25M post-money buys 20%.
Post-money framing is how funds think about ownership targets, and it is the convention of the standard post-money SAFE. Most reported round valuations in the press are post-money unless stated otherwise.