Work backwards from risk tolerance and diversification. Many angels cap startup exposure to a single‑digit share of net worth (e.g., 5% or less), then aim to spread that across 15–30+ deals over a few years. Why? Early‑stage returns follow a power law: a few outliers drive most of the gains, so a larger portfolio increases the odds you’ll hold a winner. Practically:
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● Set a total budget you can afford to lose.
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● Target a portfolio count (e.g., 20–40 initial positions).
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● Divide: initial check = total budget × ~50% / number of target initial deals; reserve the other ~50% for follow‑ons into your best performers. (Your reserve ratio can vary by strategy.)

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If you invest through syndicates or funds, platform minimums and fees may affect check sizes. If you lead or join SPVs, you might write larger checks. There’s no “right” number, but under‑diversified portfolios (e.g., <5 deals) statistically underperform, while broader portfolios tend to see better typical outcomes. Match your check sizes to your plan so you don’t run out of capital before you’ve built breadth.