Subscriber Lifetime Value: The Number That Changes Every Decision

Six months into my first toll position, another operator asked me a question over coffee that stopped me mid-sip.

“What’s the most you’d pay for one subscriber?”

I stared at him. I had no idea. I knew my list was growing. I knew revenue was climbing. I could tell you my open rate to two decimal places. But the maximum dollar amount I should spend to acquire a single email address? Blank.

He pulled out his phone, showed me a spreadsheet, and pointed to one number. “Every subscriber on my list is worth $26.40 over their lifetime. I know that because I measured it. So I know that any acquisition channel under $8 per subscriber is a guaranteed win. That’s why I’m running paid ads and you’re not.”

I drove home and spent the entire evening doing math I should have done months earlier. Subscriber Lifetime Value (SLV) — the total revenue a subscriber generates over their entire active lifespan on your list, from capture to unsubscribe or permanent dormancy.

Once I calculated mine, every decision in the portfolio got clearer overnight.

Two operators at a coffee shop, one showing a single number on his phone screen while the other stares blankly, mid-sip

How to calculate SLV

The simple version (good enough for most operators):

SLV = Average RPS × Average subscriber lifespan (in months)

If your RPS is $1.80/month and your average subscriber stays active for 14 months:

SLV = $1.80 × 14 = $25.20

Each subscriber, on average, generates $25.20 in total revenue over their time on your list.

Subscriber Lifetime Value Calculator fallback for Substack: estimate lifetime value as:

average monthly RPS x average subscriber lifespan

Default example from the live calculator:

$1.80 average monthly RPS
14-month average subscriber lifespan
$4.00 acquisition cost per subscriber
7% monthly churn

That produces a $25.20 SLV, a 6.3x SLV-to-CAC ratio, a 2.2-month payback period, and $21.20 in net lifetime profit per subscriber.

Run the interactive version on Toll Stack: Subscriber Lifetime Value Calculator

interactive calculator

Subscriber Lifetime Value Calculator

Calculate what each subscriber is worth over their entire time on your list.

Avg Monthly RPS ($)

Avg Lifespan (months)

Acquisition Cost / Sub ($)

Monthly Churn Rate (%)

Lifetime Economics

Subscriber lifetime value $25.20

SLV-to-CAC ratio 6.3x

Payback period (months) 2.2

Net lifetime profit per subscriber $21.20

Subscriber LTV: $25.20

The more precise version (for operators who want to account for decay):

SLV = Σ (Monthly RPS × Retention rate at month N) for N = 1 to 24

This accounts for the fact that not every subscriber stays 14 months — some leave at month 2, some stay 36 months. The retention-adjusted calculation is more accurate but requires cohort tracking.

Practical cohort example:

Month	Subscribers remaining	RPS	Revenue
1	100%	$1.80	$1.80
3	85%	$1.80	$1.53
6	72%	$1.90	$1.37
12	55%	$2.00	$1.10
18	40%	$2.10	$0.84
24	28%	$2.10	$0.59

Cumulative SLV at 24 months: ~$22-28 (depending on decay curve shape)

Note: RPS increases over time for the surviving cohort — because the people who stay are the ones who buy. This is selection bias working in your favor.

This article continues for paid subscribers with how SLV informs acquisition decisions, the SLV-to-CAC ratio that determines position health, segment-level SLV analysis (not all subscribers are worth the same), how to increase SLV through retention and monetization improvements, and the connection between SLV and portfolio valuation.

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Subscriber Lifetime Value: The Number That Changes Every Decision

How to calculate SLV

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