The Magic Number: A Founder's Guide to Making It Land
The magic number is the leading indicator that often moves before NRR or burn multiple do — which is why Series B partners watch it so closely. Net new ARR in a quarter divided by sales and marketing spend in the prior quarter. Above 1.0 means double down; below 0.75 signals the sales motion has a problem the founder needs to name.
The short answer
Magic number is calculated as net new ARR added in a quarter divided by sales and marketing spend in the prior quarter, multiplied by four to annualise. The lag matters — sales and marketing spend takes one to two quarters to convert into closed revenue, so the prior-quarter denominator captures the actual investment that produced the current-quarter result. Above 1.0 says every pound spent on sales and marketing is producing more than a pound of annualised recurring revenue; partners read this as a signal to deploy more capital. Below 0.75 says the sales motion is bleeding capital, which is a different conversation entirely.
Key Takeaway: Magic number is a leading indicator that moves before NRR and burn multiple do. Founders who track it monthly know whether the quarter is in trouble in week six. Founders who only track it post-close are reading a number that is already three months stale.
Directional bands drawn from SaaS index conventions and Series B underwriting practice 2024-26.
Why most founders get this wrong
The most common error is using same-quarter spend in the denominator rather than prior-quarter spend. Same-quarter spend understates the investment that produced the result, because the actual conversion lag is one to two quarters for most enterprise sales motions. The same-quarter version inflates the magic number in healthy quarters and deflates it in slow quarters, which masks the underlying trend partners care about. The prior-quarter convention is what partners audit against.
The second error is the use of gross new ARR rather than net new ARR in the numerator. Magic number is meant to test whether sales and marketing spend is producing growth net of churn and downsell — that is the relevant question for a Series B underwriter deciding whether more capital deployed produces more durable growth. Founders who use gross new ARR present a number that overstates the actual net contribution of the sales motion. Partners recalculate to net.
The third error is conflating "low magic number" with "spending too much on sales and marketing". Sometimes that is the answer — the sales motion is genuinely inefficient. But sometimes the magic number is low because of weak product-market fit (no amount of sales spend can make a wrongly-priced or wrongly-positioned product land), weak retention pulling on the net component, or a deliberate investment in market education that has a longer payback than the metric assumes. The diagnosis matters because the response differs.
Warning: A magic number sliding from 1.1 to 0.6 over four quarters is rarely a sales-team problem. The diagnosis usually sits upstream — in pricing, positioning, or the product itself. Founders who fire the head of sales when the magic number deteriorates often discover a year later that the metric did not improve, because the head of sales was not the cause.
What "sales and marketing spend" includes
Fully-loaded S&M cost: salaries (with employer taxes and benefits), commissions paid, marketing program spend, agency fees, sales tooling and infrastructure, attributable portion of revenue operations and customer success acquisition cost. Founders who exclude commissions on the basis that they are "variable" or exclude RevOps on the basis that it is "infrastructure" produce a flattering version of the metric that partners back out.
What is not included: customer success cost related to retention and expansion (this belongs to the net retention metric, not the new-logo acquisition metric), product engineering, general and administrative costs.
What "good" looks like
Series B benchmarks for the magic number have tightened in line with the broader Series B efficiency bar. The 2025-26 cycle expects the metric to sit consistently above 0.75 with a positive trajectory; partners use the four-quarter trailing average rather than the most recent quarter to damp the seasonal noise.
| Magic number (4Q trailing) | Signal | What partners typically do |
|---|---|---|
| > 1.5 | Exceptional sales efficiency | Deploy aggressively; price round at premium |
| 1.0-1.5 | Strong; double-down band | Active engagement; price within sector medians |
| 0.75-1.0 | Acceptable; narrative carries | Engage if other metrics support; expect questions on sales motion |
| 0.5-0.75 | Underwhelming; needs explicit thesis | Engagement contingent on diagnosis and credible improvement plan |
| < 0.5 | Sales motion or PMF problem | Most pass; some engage on bridge-style structure to fund the diagnosis |
The six-week founder diagnostic
The fastest founder-grade diagnostic on a low magic number is a six-week sequence: week 1-2, segment the number by sales segment (SMB vs mid-market vs enterprise) and motion (inbound vs outbound vs partner-sourced) — the segment-level numbers usually expose where the spend is being burned. Week 3-4, audit the conversion funnel by segment — top of funnel, qualified opportunity, closed-won — and identify which transition is the binding constraint. Week 5-6, run the test of whether the binding constraint is a sales-team capability problem, a product-or-pricing problem, or an ICP-targeting problem; the response sequence depends entirely on which one it is.
What the metric does not tell you
Magic number is silent on retention quality, expansion-revenue capacity, and the durability of the sales motion at scale. A business with a strong magic number and weak NRR is acquiring fast and leaking faster — partners spot this in five minutes from the cohort chart. A business with a weak magic number and strong NRR has a customer success organisation that is doing the work the new-logo acquisition motion is failing to do. Both patterns require a different Series B narrative than "we just need more capital".
How to apply it to your round
The magic number is a metric founders should be tracking monthly with quarterly headline reporting, not just running for the deck. The board cadence work is what surfaces the deterioration patterns early enough to act on them.
Track monthly, report quarterly. The monthly trend exposes the deterioration before the quarterly headline does. If the rolling-three-month magic number has dropped 0.2 in two consecutive months, the diagnosis work should already be underway by month three — not at the end of the quarter when the partner conversation has begun.
Segment by sales motion. The blended number masks the actual story. Inbound vs outbound vs partner-sourced often have magic numbers that differ by 0.5+; the segmentation tells the partner where the unit economics are actually working and where the investment thesis sits.
Pair with the cohort retention chart. A magic number of 1.2 paired with NRR of 90% is a Series B pass. A magic number of 0.9 paired with NRR of 130% is a Series B yes. The two metrics together tell the durability story; either alone is misleading.
Connect to the underlying drivers. Magic number is the observable output of brand and reputation (inbound efficiency), content and IP (lead generation cost), and ecosystem partnerships (channel-sourced ARR). Founders who can name the drivers behind the metric communicate operator maturity; founders who treat it as a sales-team metric communicate the opposite.
Presentation that loses partners
- Same-quarter denominator
- Gross new ARR numerator
- Single-quarter snapshot
- Blended across all sales motions
- "We need to fix sales" as the diagnosis
Presentation that earns engagement
- Prior-quarter denominator
- Net new ARR numerator
- Four-quarter trailing average + chart
- Decomposed by motion (inbound/outbound/partner)
- Explicit diagnosis of binding constraint
The Bottom Line
Magic number is the leading indicator that moves before the lagging headline metrics do. The construction discipline (prior-quarter denominator, net ARR numerator, segment-level decomposition) is what makes the metric useful operationally and presentable in the partner conversation. Founders who run their business to the magic number monthly bring the partner a thesis the partner can underwrite; founders who calculate it for the deck bring the partner a number the partner audits.
Related reading
Magic number is one of five Series B headline metrics and is best read alongside the others. For the broader bar: the Series B efficiency bar in 2025. For the combined growth-and-margin number: Rule of 40 at Series B. For the capital efficiency partner: burn multiple: what investors want to see. For the retention partner: from 108% to 128% NRR. For the next-step expansion-motion build: building the expansion motion before Series B. For the underlying intangible drivers behind sales efficiency: The Opagio 12 value drivers.
Read your magic number the way the partner will
Eight minutes. Twelve drivers. The starting view of where your sales-efficiency leading indicator sits — and which intangible drivers compound it toward the double-down band.