SaaS Magic Number Calculator
Calculate the SaaS magic number from quarterly revenue and sales and marketing spend, with the standard 0.5 / 0.75 interpretation bands and implied CAC payback.
Quarterly revenue and sales & marketing spend
Columns are quarter label, quarter revenue, and that quarter's sales & marketing spend. At least two quarters are needed.
0.80 — Between 0.75 and 1.0 — the widely used threshold for 'keep spending'. Growth is paying for itself at a reasonable rate.
| Quarter | Revenue | S&M spend | Revenue added | Annualised (×4) | Magic number |
|---|---|---|---|---|---|
| Q1 | $10,000,000 | $4,000,000 | — | — | — |
| Q2 | $11,000,000 | $4,400,000 | $1,000,000 | $4,000,000 | 1.00 |
| Q3 | $12,100,000 | $5,000,000 | $1,100,000 | $4,400,000 | 1.00 |
| Q4 | $13,100,000 | $5,200,000 | $1,000,000 | $4,000,000 | 0.80 |
Magic number = (this quarter's revenue − last quarter's revenue) × 4 ÷ last quarter's S&M spend · implied CAC payback (months) = 12 ÷ magic number
Worked example: revenue rises from $10,000,000 to $11,000,000while the prior quarter's sales and marketing spend was $4,000,000. That is (11M − 10M) × 4 ÷ 4M = 1.00, which implies a 12-month payback on go-to-market spend.
The magic number deliberately compares this quarter's revenue gain against lastquarter's spend, on the assumption that sales effort takes about a quarter to convert. It is a blunt instrument: it credits all revenue growth to sales and marketing, ignores expansion versus new business, and gets noisy for companies under roughly $1,000,000 a quarter. The 50%/75% interpretation bands are conventions, not laws. Everything is calculated in your browser and nothing is uploaded.
What is the SaaS Magic Number Calculator?
The magic number measures how much annual revenue each dollar of sales and marketing buys. Take the revenue you added this quarter, annualise it by multiplying by four, and divide by what you spent on sales and marketing the quarter before — the lag is deliberate, because go-to-market effort takes about a quarter to show up as revenue.
- Magic number for every quarter transition in one table
- Standard bands: below 0.5, 0.5 to 0.75, and above 0.75
- Implied CAC payback in months derived from the magic number
- Gross-margin-adjusted magic number alongside the headline figure
- Add or remove quarters with editable labels
- Entirely client-side — your revenue data never leaves the browser
How to use the SaaS Magic Number Calculator
- 1
Pick a currency and enter your gross margin for the margin-adjusted variant.
- 2
Fill in each quarter's label, revenue and sales and marketing spend — at least two quarters.
- 3
Use Add quarter to extend the series, or the bin icon to drop a row.
- 4
Read the latest magic number, its interpretation band and the implied CAC payback.
- 5
Scan the table to see how the magic number has moved quarter by quarter.
About the SaaS Magic Number Calculator
The magic number measures how much annual revenue each dollar of sales and marketing buys. Take the revenue you added this quarter, annualise it by multiplying by four, and divide by what you spent on sales and marketing the quarter before — the lag is deliberate, because go-to-market effort takes about a quarter to show up as revenue.
This calculator does it across as many quarters as you want to enter, so you can see whether efficiency is improving or quietly decaying. It applies the standard interpretation bands used by growth investors, converts the result into an implied CAC payback period in months, and shows a gross-margin-adjusted version for the investors who prefer it.
Add or remove quarters freely, label them however you like, and read the trend in the table below rather than fixating on any single quarter. Every figure is calculated locally in your browser, so none of your revenue or spend data is ever uploaded, stored or shared — which makes it safe to use with figures straight out of a board pack.
Frequently asked questions
What is a good SaaS magic number?
The convention is that below 0.5 you should pause and fix efficiency, between 0.5 and 0.75 you optimise before accelerating, and above 0.75 you keep spending. Above 1.0 means each dollar of sales and marketing buys more than a dollar of annual recurring revenue, which usually argues for spending more, not less.
Why does the magic number use last quarter's spend?
Because sales and marketing effort rarely converts in the same quarter it is spent. Comparing this quarter's revenue gain against the previous quarter's spend builds in roughly one quarter of lag, which matches how most B2B sales cycles actually behave. It is an approximation, and it fits long enterprise cycles badly.
How does the magic number relate to CAC payback?
They are two views of the same efficiency. Because the magic number annualises the new revenue, the implied payback period in months is simply 12 divided by the magic number — a magic number of 1.0 means roughly a 12-month payback, and 2.0 means about six months.
What are the limitations of the magic number?
It credits every bit of revenue growth to sales and marketing, ignores whether that growth came from new logos or expansion within existing accounts, and gets very noisy for small companies where one big deal swings a quarter. Treat it as a directional trend across several quarters, not a verdict on any single one.
Should I use gross revenue or net new ARR?
The classic formula uses the change in reported quarterly revenue, which is what this tool asks for. Some investors prefer net new ARR, which strips out services and one-off revenue. Both are shown as a trend here — the important thing is to use the same definition consistently across quarters.
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