Round size is the total capital raised in a financing, determined by balancing runway, milestones, dilution, and capital efficiency. Key factors include runway needs (typically 18-24 months of operating cash), capital required to hit milestones for the next round, dilution tolerance (more capital means more dilution at given valuation), valuation impact (very large rounds at high valuations create future pressure), and capital efficiency (raising more than needed creates "fat" operations). Right-sizing is one of the most-important fundraising decisions and one founders frequently get wrong by raising too much (excess dilution, future pressure) or too little (insufficient runway, premature next-round fundraise). It's the dial that...