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GTM Fundamentals · intermediate · node 5.7

Magic number / sales efficiency

Magic number = (New ARR this quarter - New ARR last quarter) / (Sales + Marketing spend this quarter). A magic number > 0.75 is good; > 1.0 is exceptional. Magic number tells whether you are scaling sales efficiently or burning through money on customer acquisition. It is a leading indicator: if magic number is 0.5, your LTV:CAC ratio is broken and you need to cut burn or improve sales conversion. Magic number changes with maturity: early-stage (raising Series A) targets 0.3–0.5 (growth is the north star); late-stage (Series D+) targets 1.0+ (profitability is the north star). Rule of 40 is the broader frame: growth rate + magic number should sum to 40 for a sustainable business.
intermediate Last updated 2026-06-25

Prerequisites

Unit economics fundamentalsCAC payback periodRule of 40

Magic number measures how efficiently you generate ARR from sales+marketing spend.

Magic number = (New ARR this quarter - New ARR last quarter) / (Sales + Marketing spend this quarter)

Example:

  • Q1 new ARR: $500k
  • Q2 new ARR: $800k
  • New ARR generated in Q2: $300k
  • Q2 S+M spend: $400k
  • Magic number: $300k / $400k = 0.75

A magic number of 0.75 means $1 of sales+marketing spend generates $0.75 of new ARR. Magic number 1.0 means breakeven (you make back your spend in new ARR the same quarter). Magic number > 1.0 is exceptional (you generate more ARR than you spend).

Thresholds:

  • < 0.3: Burning cash unsustainably. Growth is not justifying spend.
  • 0.3–0.75: Growth-focused, venture-scale. Spending ahead of ARR generation but acceptable if you are in hyper-growth (40%+ YoY) and have runway.
  • 0.75–1.0: Efficient growth. You are generating nearly as much ARR as you spend, leaving room for margins.

  • 1.0: Exceptional. Rare in pre-Series C; common in mature, sales-heavy businesses.

Magic number is a lagging indicator. If it drops from 0.8 to 0.6 in Q2, it’s a signal that something broke 2–3 months ago: lower lead quality, lower close rates, lower ACV, or longer sales cycles. Investigate immediately.

Magic number vs. Rule of 40:

The Rule of 40 says: Growth Rate + Magic Number = 40 for a sustainable business.

  • 40% growth business can afford 0% magic number (pure growth; no focus on efficiency yet).
  • 20% growth business should target 20% magic number.
  • 10% growth business must hit 30% magic number to be sustainable.

A business at 50% growth but 0% magic number is unsustainable: growth is masking unit economics collapse. A business at 10% growth and 10% magic number is dying: it needs to either accelerate growth or cut burn.

Improving magic number requires: higher close rates (sales training, better qualification), shorter sales cycles (product improvements, buyer enablement), higher ACV (upselling, upmarket positioning), or lower sales+marketing spend (product virality, inbound, self-serve).

Most SaaS companies improve magic number by ~0.1 per year as they mature, CAC payback shortens, and inbound grows relative to outbound.

Key takeaways

  • Magic number = (new ARR this quarter - new ARR last quarter) / (S+M spend this quarter).
  • Thresholds: &lt;0.3 = burning cash unsustainably; 0.3–0.75 = growth-focused but risky; 0.75+ = efficient; 1.0+ = exceptional.
  • Magic number is a lagging indicator of funnel health: if it drops from 0.8 to 0.6, something broke in lead quality, close rate, or ACV three months ago.
  • Rule of 40: growth rate + magic number = 40 for a sustainable business. A 40% growth business can afford 0% magic number; a 10% growth business needs 30% magic number.

Related concepts

LTV:CAC ratioSustainability & profitability

How to cite this

@misc{shalvi_gtm_fundamentals_magic_number_sales_efficiency_2026,
  author = {Singh, Shalvi},
  title  = {Magic number / sales efficiency},
  year   = {2026},
  url    = {https://shalvisingh.com/gtm/fundamentals/magic-number-sales-efficiency},
  note   = {GTM World Model — GTM Fundamentals}
}

Singh, Shalvi. "Magic number / sales efficiency — GTM Fundamentals." shalvisingh.com, 2026. https://shalvisingh.com/gtm/fundamentals/magic-number-sales-efficiency