How the math works
The calculator works backwards from your goal, one step at a time:
- Prospects = meetings ÷ (positive reply rate × share of positive replies that book). At a 2% positive reply rate and half of those booking, every meeting takes 100 prospects.
- Emails = prospects × emails in the sequence, spread across your sending days.
- Mailboxes = emails per day ÷ what one mailbox should send per day, rounded up.
- Domains = mailboxes ÷ mailboxes per domain, rounded up.
Deal value is optional. Fill it in to see what the plan is worth, which is the number that decides whether the mailboxes, domains and data are worth paying for.
What the calculator leaves out
- Bounces and invalid contacts. Addresses that bounce still cost a send and hurt the mailbox. Verify the list first and add a margin to the prospect count for addresses you will remove.
- Time lag. Replies to the last step arrive weeks after the first email, so a new campaign takes about a sequence's length to reach the steady state shown here.
- Replies you must answer. At the volumes above, someone has to handle every reply within hours.
Using it to plan
Change one input at a time
The outputs move in proportion to the reply rate: double the reply rate and you need half the prospects, half the mailboxes and half the domains. Better targeting and copy almost always beat buying more sending capacity. Check your copy with the spam word checker before you scale.
Keep per-mailbox volume conservative
Spreading volume over more mailboxes is cheaper than recovering a burned domain. If a domain lands on a blocklist, the blacklist checker shows which list and how to request removal.
Set up every new domain properly
Each sending domain needs its own SPF, DKIM and DMARC records. The SPF and DMARC generator writes them for your provider, and the deliverability checker confirms they are live.