How to calculate the SaaS magic number
The magic number measures sales and marketing efficiency: how much new recurring revenue each dollar of go-to-market spend produces. It tells you whether to press the accelerator on growth investment or fix efficiency first.
Short answer
Calculate the SaaS magic number by dividing the net new ARR added in a quarter by the sales and marketing spend of the prior quarter. For example, 500,000 dollars of net new ARR from 400,000 dollars of prior-quarter spend is a magic number of 1.25. Above 0.75 generally signals efficient, scalable growth worth investing into.
Step by step
Find net new ARR for the quarter
Take the increase in ARR during the quarter (new plus expansion minus churn), annualized if you started from quarterly recurring revenue.
Find prior-quarter go-to-market spend
Use the prior quarter's sales and marketing spend, reflecting the lag between spend and the revenue it produces.
- Magic number = net new ARR / prior quarter S&M spend
- Above 0.75 is generally efficient
- Use the prior quarter's spend to respect the lag
Divide and interpret
A result above roughly 0.75 suggests efficient growth you can invest into; below it, fix efficiency before spending more.
Read it with payback and LTV to CAC
The magic number is a fast proxy; confirm with payback period and LTV to CAC before making big spend decisions.
Trend it across quarters
Track it over several quarters to smooth noise and see whether efficiency is improving or eroding.
How Ardovo helps
Ardovo derives net new ARR and ties it to go-to-market spend by quarter, so Rook can report the magic number alongside payback and LTV to CAC, giving you a full efficiency picture instead of one noisy ratio.
Frequently asked questions
What is a good magic number?
Above 0.75 generally indicates efficient growth worth investing into, and above 1.0 is strong. Below 0.75 suggests your go-to-market is not yet efficient enough to scale spend, so you should improve conversion or retention first.
Why use the prior quarter's spend?
Because there is a lag between spending on sales and marketing and the revenue it generates. Pairing this quarter's net new ARR with last quarter's spend respects that delay and gives a more honest efficiency read.
Is the magic number enough to decide spend?
No, treat it as a fast proxy. Confirm with CAC payback period and LTV to CAC before making major investment decisions, since the magic number is noisy quarter to quarter and does not capture cash-flow timing or lifetime profitability.