The Efficiency Story That Unlocks Series B

Round Ready Academy — Lesson 9 of 11

The Series B market of 2025 and 2026 is not the market of 2021. The growth-at-all-costs thesis that underwrote the 2021 cohort is gone; the efficiency-at-scale thesis has replaced it. Series B partners now ask questions that were reserved for late-stage growth just four years ago.

This lesson is about the efficiency story — what it contains, why the bar has moved, and how to present the benchmarks that now determine the Series B range.

Why the Bar Moved — a Short Diagnosis

Three structural shifts have moved the Series B bar over the last four years.

First, the cost of capital rose. Rates moved from zero to meaningful, which changed how investors discount future cash flows. A business whose value is in 2028 cash flows is worth less in 2026 than it was in 2021 — not because the business is worse, but because the discount is harsher.

Second, public-market SaaS multiples compressed. The public comparables that underwrite Series B private multiples fell from 20x ARR at the 2021 peak to 7x-10x at the 2025/26 norm. Private multiples compressed with them.

Third, the distributions of outcomes from the 2019-2021 Series B cohort became visible. A significant share of those rounds either raised flat/down bridges or did not raise at all through 2023-2024. The Series B partners writing today's cheques have seen that pattern and have adjusted their underwriting.

The practical effect: a Series B that would have required 80%+ growth and ignorable unit economics in 2021 now requires 50-70% growth plus clear efficiency evidence — or 40-50% growth plus exceptional efficiency evidence. The trade-off has moved.

The Rule of 40 — and Where It Moved

The Rule of 40 is the headline efficiency metric at Series B: growth rate plus free-cash-flow margin (or, in some formulations, EBITDA margin), summed, should clear a threshold. For much of the post-2010 SaaS era, that threshold was 40%.

Across the Series B cohort in 2024 and 2025, the bar shifted. The median Series B closing at competitive terms now tracks closer to 45%+ on the Rule of 40, with the top quartile at 55%+. This is a directional claim supported by the annual benchmarks published by Bessemer Venture Partners' State of the Cloud and Battery Ventures' OpenCloud report. The exact threshold varies by source and by stage definition, but the direction — up — is consistent.