There is no universal list size that guarantees 50 sales. You can estimate the audience you need from your own campaign data, provided you use consistent definitions for each rate.
Example: if every email is delivered, 3% of delivered emails generate a unique click, and 2% of those clickers buy one unit, you need approximately 83,334 delivered emails for an expected 50 sales. This is a hypothetical illustration, not an industry average or a guarantee.
The simple formula
When click-through rate (CTR) is unique clicks divided by delivered emails, and purchase conversion rate is orders divided by unique clickers:
Delivered emails needed = target orders ÷ (CTR × purchase conversion rate)
Use rates as decimals. Round the final result up to a whole delivered email:
| Step |
Calculation |
Expected result |
| Delivered emails |
50 ÷ (0.03 × 0.02) |
83,333.33 |
| Unique clickers |
83,334 × 0.03 |
About 2,500 |
| Orders |
2,500 × 0.02 |
About 50 |
This assumes one unit per order and that each clicker can make at most one counted purchase. If customers often buy multiple units, account for units per order separately. The output is an expectation based on the inputs, not an exact forecast.
To estimate the subscribers to send to, divide delivered emails by your delivery rate. At a hypothetical 95% delivery rate, 83,334 ÷ 0.95 gives approximately 87,720 subscribers. Account for unsubscribes, suppression, consent and list eligibility before planning a send.
CTR is not click-to-open rate
The denominator matters:
- CTR: unique clickers ÷ delivered emails.
- Click-to-open rate (CTOR): unique clickers ÷ unique openers.
- Purchase conversion rate: purchases ÷ unique clickers in this example.
Do not multiply an open rate by CTR when CTR already uses delivered emails as its denominator: doing so counts the open stage twice.
If you instead have a 20% open rate, a 3% CTOR and a 2% click-to-purchase conversion rate, the calculation is 50 ÷ (0.20 × 0.03 × 0.02), or 416,667 delivered emails after rounding up. A 3% CTOR is not the same input as a 3% CTR.
Open tracking is imperfect. For example, Apple Mail Privacy Protection affects open-rate measurement, so use observed click and purchase data where possible. Mailchimp's benchmark notes also explain this limitation.
Try your own scenarios
These are illustrations using CTR per delivered email, a conversion rate per unique clicker, and one unit per order:
| CTR |
Purchase conversion |
Delivered emails for 50 expected orders |
| 1% |
1% |
500,000 |
| 3% |
2% |
83,334 |
| 5% |
5% |
20,000 |
Small changes to either rate can materially change the estimate. Use several comparable campaigns to choose inputs, and test a range rather than treating a single past campaign as a prediction.
Improve the result
- Segment by genuine interest and send only to eligible subscribers.
- Make the email's offer and call to action consistent with the landing page.
- Measure delivered emails, unique clickers and purchases over the same attribution window.
- Test changes against comparable campaigns, and consider returns, product costs and attribution when assessing profit.
Use the click-through rate calculator to calculate CTR, the conversion rate calculator to check your conversion rate, and the email ROI calculator to assess campaign costs and revenue. The list breakeven calculator answers a different question: how subscriber revenue compares with list-growth costs.
