How much runway should your raise actually buy?

Ask ten founders how they sized their round and most will describe a negotiation with their own optimism: a number big enough to feel safe, small enough to feel raisable, rounded to something that sounds intentional.

Investors can smell a round number arrived at this way, because they all check it against the same convention: a raise should buy roughly 18 to 24 months of runway. The convention isn't arbitrary — it's built backwards from how fundraising actually works:

  • Your next raise takes roughly six months of focused work to close.
  • Before that, you need something to show — which means the milestone that justifies the next round needs to be hit with time to spare.
  • 18–24 months is the window that fits milestone + fundraise + buffer without forcing you to raise again from weakness.

Less than that and you're not buying execution time, you're buying a countdown to a desperate raise. Much more and the question becomes why you're taking dilution now for money you won't deploy for two years.

The credible version of an ask, then, is arithmetic rather than aspiration:

  1. Monthly burn at the team size this round actually funds — not today's burn.
  2. × 18 to 24 months.
  3. Sanity-checked against the milestone: does this budget plausibly reach the metric that unlocks the next round — the revenue level, the usage curve, the regulatory gate?

When an investor pushes on your number, the defensible answer sounds like: "$400k is 20 months at our post-hire burn of $20k/month, and our Series-A conversations start at $50k MRR, which this window reaches at our current growth rate." Every part of that sentence can be interrogated, which is precisely what makes it trustworthy.

Notice what this requires: a financial model with visible assumptions. That's why "the ask" and "financial model" are separate checks in the Investor-Readiness Score — an ask without a model behind it is a wish with a dollar sign.

Build the model first — the financial model tool on StartupKit is free — then let the ask fall out of the arithmetic. Rounds sized backwards from milestones get funded. Rounds sized forwards from optimism get questions.