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Email Reach Calculator

The Email Reach Calculator estimates how many unique recipients are likely to see at least one delivered message during a campaign. It starts with your sendable audience, adjusts for deliverability, and then accounts for the fact that repeat sends often reach many of the same people rather than an entirely new audience each time.

Use the estimate when planning campaign scale, comparing list segments, or setting realistic awareness goals. The result is not the same as total deliveries or opens: reach is an estimate of distinct inboxes exposed to one or more messages. Because overlap varies by sending strategy, the calculator lets you state an expected repeat-audience overlap instead of assuming every send reaches a different person.

Calculator inputs

contacts
%
sends
%
Result
—
unique recipients
Delivered messages—
Estimated unique reach—
Average frequency—

1. Enter the sendable audience

Use the number of contacts eligible to receive the campaign after suppressions and exclusions.

2. Set the delivery rate

Enter the expected percentage of attempted sends that will be accepted by receiving mail servers.

3. Add campaign frequency

Enter how many messages each contact is scheduled to receive during the period.

4. Estimate repeat overlap

Use a higher overlap when the same list receives every message and a lower overlap when sends target different segments.

5. Review reach and frequency

Compare estimated unique reach with delivered messages and average exposure frequency.

Delivered messages = Audience × Delivery rate × Sends
Estimated reach = min(Audience, First-send deliveries + Incremental repeat-send reach)
Incremental repeat-send reach = (Sends − 1) × First-send deliveries × (1 − Overlap rate)

Delivery rate and overlap rate are entered as percentages and converted to decimals. The model assumes the first send establishes the initial reachable audience and each later send adds only the non-overlapping share. Actual unique reach depends on list churn, segment rules, mailbox placement, and identity matching.

What the result means

The main result estimates distinct recipients exposed to at least one delivered email during the campaign period.

Treat this as a planning estimate rather than a platform-reported unique-user count.

Given

  • 50,000 sendable contacts
  • 97% delivery rate
  • 3 sends per contact
  • 85% repeat-send overlap

Calculation

First-send deliveries = 50,000 × 0.97 = 48,500. Incremental reach = 2 × 48,500 × (1 − 0.85) = 14,550. Reach is capped at the 50,000-contact audience.

Result

Estimated unique reach = 50,000 recipients. Delivered messages = 145,500, so average frequency = 145,500 ÷ 50,000 = 2.91×.

Interpretation

The campaign is expected to touch nearly the full sendable list, with each reached recipient receiving about 2.9 delivered messages on average.

Why can reach be lower than delivered messages?

Delivered messages count every accepted email, including repeated messages to the same contact. Reach counts each recipient only once.

What overlap rate should I use?

Use a value near 100% when nearly identical lists receive each send. Lower it when campaigns rotate through substantially different segments.

Does reach equal opens?

No. Reach estimates delivered exposure, while opens require tracking activity and may be affected by privacy features and image loading.

Can estimated reach exceed list size?

No. The calculator caps unique reach at the sendable audience because one contact cannot count as more than one unique recipient.

How is this different from frequency?

Reach measures how many distinct recipients are exposed. Frequency measures the average number of delivered messages per reached recipient.