SaaS Magic Number Calculator
Calculate the SaaS magic number to measure sales and marketing efficiency — how much new recurring revenue each unit of go-to-market spend generates.
✨ SaaS Metrics📐 Magic number = (current quarter ARR − prior quarter ARR) / prior quarter S&M spend💼 Business
Current quarter ARR
Prior quarter ARR
Prior quarter sales & marketing spend
Gross margin (%, optional)
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| SaaS Magic Number Calculator | — | Magic number = (current quarter ARR − prior quarter ARR) / prior quarter S&M spend | ratio |
Step-by-Step Examples
Example 1
Efficient Growth
Q4 ARR 4,400,000, Q3 ARR 4,000,000, Q3 S&M spend 500,000.
- Net new ARR = 4,400,000 − 4,000,000 = 400,000
- Magic number = 400,000 / 500,000
- Magic number = 0.80
✓ 0.80 — reasonable efficiency
Example 2
Above 1.0
Q2 ARR 2,700,000, Q1 ARR 2,300,000, Q1 S&M spend 350,000.
- Net new ARR = 400,000
- Magic number = 400,000 / 350,000 = 1.14
- Above 1.0 generally supports increasing spend
✓ 1.14 — efficient, scale up
Example 3
Inefficient
Q3 ARR 6,150,000, Q2 ARR 6,000,000, Q2 S&M spend 800,000.
- Net new ARR = 150,000
- Magic number = 150,000 / 800,000 = 0.19
- Well below 0.5 — spending more would compound the inefficiency
✓ 0.19 — fix before scaling
Real-World Applications
Spend Decisions
The magic number is a practical guide to whether increasing sales and marketing spend will generate proportionate returns.
Lag Adjustment
Using prior-quarter spend against current-quarter ARR growth reflects the real delay between spending and revenue arriving.
Board Reporting
It is a standard efficiency metric in subscription business board packs and investor updates.
Complement to CAC
Magic number captures the whole go-to-market motion including retention effects, where CAC looks only at new customer acquisition.
Common Mistakes to Avoid
⚠️
Reading a low magic number as a reason to cut spend
It may instead indicate a targeting, positioning, or product problem. Cutting spend without diagnosing the cause simply shrinks the business.
⚠️
Ignoring the quarterly lag
Using same-quarter spend overstates efficiency, since much of that spend has not yet converted to revenue.
⚠️
Applying it to very early-stage companies
With small absolute ARR and lumpy deals, quarterly magic numbers swing wildly and carry little signal.
Frequently Asked Questions
What is the SaaS magic number? ▾
A sales efficiency ratio dividing the change in ARR over a quarter by the prior quarter's sales and marketing spend.
What is a good magic number? ▾
Above 1.0 is generally considered efficient and supportive of increasing spend. Below 0.5 suggests fixing the go-to-market motion before scaling.
Why use prior quarter spend? ▾
Because there is a lag between spending on acquisition and the resulting revenue landing. Matching current revenue to prior spend reflects that reality.
How does it differ from CAC? ▾
CAC measures cost per new customer acquired. The magic number captures the net effect of the whole go-to-market motion, including expansion and churn.
Should ARR or revenue be used? ▾
ARR, since the metric is designed for recurring revenue businesses. Using total revenue including one-off services distorts the result.