Cold email campaign calculator

How the calculation works

Combined daily capacity equals available mailboxes multiplied by the spare daily cap per mailbox. Divide eligible prospects by that capacity and round up to estimate the minimum number of sending days for first emails. If 100 eligible prospects share one mailbox with 10 spare slots per day, their first emails need at least 10 sending days.

For a multi-message plan, maximum message slots equal prospects multiplied by the maximum messages per prospect. Divide those slots by daily capacity and round up for the capacity lower bound. For example, three messages each for 100 prospects require up to 300 slots. At 10 slots per day, that is at least 30 sending days of capacity. It is not a sequence completion date: waiting periods between steps can extend the calendar.

Use capacity you actually have

Start with the lower of the limits that apply to your campaign and mailboxes. Subtract capacity reserved for other work. This calculator assumes the same remaining daily allowance for each mailbox and no additional campaign-wide bottleneck. If your campaign has a lower shared cap, use that constraint when reviewing the result instead of assuming all mailbox capacity is available.

A mailbox count does not establish permission to send or a safe sending rate. The tool does not inspect your account, check sender reputation, verify recipient mailboxes, schedule messages or launch campaigns. Empty or fractional inputs produce a validation message rather than a misleading result.

Why the actual schedule can differ

Weekends, holidays, time windows, timezone choices, pauses and sequence delays affect elapsed time. Replies, bounces and opt-outs can remove later steps. A plan with enough capacity can still have poor targeting or an unclear offer. No part of this arithmetic forecasts inbox placement, replies or customers.

Turn a capacity estimate into a small pilot

Choose one audience, one clear offer and a small eligible list. Document the source and verification evidence for each recipient. Prepare the exact subject and body, inspect the sender and schedule, and follow your campaign review requirements. Compare actual sends and interested replies with the plan before expanding the audience.