Phase I vs. Phase II vs. Phase III, explained

• Phase I tests the technical merit, feasibility and commercial potential of an idea. It's a smaller award over a short period (typically 6–12 months).
• Phase II continues the R&D started in Phase I. It's a larger award, typically over about two years, and is generally open only to Phase I awardees (some agencies allow “Direct to Phase II”).
• Phase III is commercialization. It isn't funded by SBIR/STTR program money; it's funded by the private sector or by other (non-SBIR) federal funding, including government contracts.

SBA publishes guideline amounts for Phase I and Phase II awards and adjusts them over time; individual agencies and topics set their own amounts. Check the specific solicitation for the amount and length of each award. You'll see a topic's phase on its SBIR Radar page (for example “Phase I”, “Phase II” or “BOTH”).

Official sources

• SBIR.gov – About (program phases)
• SBIR/STTR Policy Directive (SBA)

This guide is a plain-English summary, not legal advice. Rules change; the solicitation and SBA policy directive govern.