Work out what an email list is worth per campaign, per month and per subscriber. Revenue per subscriber is the number that tells you whether growing the list or improving the emails is the better use of your time.
Revenue per subscriber is the real metric
List size is the number people quote and the least useful one. A list of two thousand engaged readers routinely outearns a list of twenty thousand who signed up for a giveaway and never opened anything since.
Revenue per subscriber strips out size entirely, which makes it comparable over time and across lists. When it rises, your emails got better. When it falls as the list grows, you are acquiring the wrong subscribers.
The funnel multiplies, so small gains compound
Four percentages multiply together here: opened, clicked, converted, and the order value. Because they multiply rather than add, improving each one slightly has a far larger combined effect than improving any single one substantially.
- Open rate is mostly the subject line and the sender name. Consistency in who the email comes from matters more than cleverness in the subject.
- Click rate is the offer and the call to action. One clear action per email outperforms several competing ones.
- Conversion rate is the landing page, not the email. If clicks are healthy and sales are not, the problem is after the click.
- Order value is pricing and bundling, and it is usually the easiest of the four to move.
Sending more is not the answer
Raising campaign frequency is the tempting lever because it multiplies the monthly figure directly in this calculator. In practice it drives unsubscribes and pushes open rates down, and the net effect is often negative within a couple of months.
Model an increase here, then ask whether your content can sustain that cadence at the same quality. If it cannot, the extra sends cost more than they earn.
Note also that open rates have become less reliable as a metric since mail providers began pre-loading images, which inflates them. Click rate is the more trustworthy signal of engagement.