Work out how fast reinvesting can grow you

What it does

Growth goes exponential on one condition: what you add each month has to grow with what you already have. Revenue has to buy more revenue. The loop you control is reinvestment: a share of MRR goes back into acquisition, at a payback you know. This playbook works out the growth rate that loop buys you, and what moves it most.

What you need

• Your payback in months (see price a channel)
• Your monthly churn rate
• The share of MRR you could put back into acquisition each month

How it works

1. 1

   Pick the share you’d reinvest

   s is the share of MRR you put into acquisition each month, all-in: tools, data, ads and people. Pick a share you could actually afford for a year.

2. 2

   Work out the growth rate

   The loop’s monthly growth rate is g = s ÷ P − c, where P is payback in months and c is monthly churn. Each doubling then takes about 0.69 ÷ g months.

   Google Sheets: paste into A1

   Share of MRR reinvested a month (s)	20%
   Payback in months (P)	2.6
   Monthly churn (c)	2%
   Monthly growth from the loop (g)	=B1/B2-B3
   Months to double	=0.69/B4

3. 3

   See which lever moves it most

   Run the sheet three times: a higher share, a shorter payback, and lower churn. For most founders, the win rate does the most, because it shortens payback, and payback divides everything.

4. 4

   Check it against your market

   Every loop meets its market. As your MRR closes in on what your segment can hold, each dollar buys less: the real rate is closer to s ÷ P × (1 − M ÷ K) − c, where K is your segment’s size in MRR (the accounts that fit, times the MRR each is worth). When growth bends, move next door: the adjacent segment, the same playbook, your logos as proof.

5. 5

   Only turn it on when the unit case holds twice

   Reinvest at scale once the channel pays back in two independent segments. A result that happens once is a coincidence with good PR.

What good looks like

You know your loop’s growth rate, the doubling time it buys, and which lever you’re pulling next quarter.

Mistakes to skip

• Reinvesting before the unit case holds. You scale the loss along with the channel.
• Assuming the cost per opportunity stays flat. Channels get pricier as you push them, so re-check payback every quarter.
• Forgetting churn. At 2% a month, a loop growing 2% a month is standing still.