How the Calculator Works
This calculator inverts the standard B2B cold-email funnel — instead of starting from how many emails you want to send, it starts from how many meetings you want to book. Each step is plain arithmetic with a benchmark you can override.
The chain in order
- Meetings ÷ reply-to-meeting rate → Replies needed
- Replies ÷ per-prospect reply rate → Prospects needed
- Prospects × sequence length → Total emails / month
- Total emails ÷ working days → Emails / day
- Daily emails ÷ per-inbox-per-day → Inboxes needed
- Inboxes ÷ inboxes-per-domain → Domains needed
Sequence length matters because every prospect receives multiple emails. A 4-touch sequence doubles your email volume vs a 2-touch one — and that doubles your inbox and domain requirement. This is the most common reason teams under-provision and burn deliverability.
Default Benchmarks (and Why)
These defaults reflect what I've seen consistently across 500+ outbound campaigns. Override them in the calculator if your historical numbers differ.
- 10% reply rate Per prospect, across the whole sequence. Below 5% usually means ICP or messaging is broken; above 15% is rare. Lever
- 25% reply → meeting Conservative. With sharp qualification, this lands closer to 35%. Lower if you're prospecting cold-cold; higher if you're working warm signals. Conversion
- 22 working days / month Standard for B2B teams. Drop to 20 if your team has Fridays off or runs 4-day weeks. Volume planning
- 30 emails / inbox / day Sustainable after 2-3 weeks of warmup. Pushing past 50 risks deliverability. Some platforms allow 100+, but reputation suffers. Deliverability ceiling
- 3 inboxes / domain Safe ratio. More than 4-5 on a single domain risks reputation cascade if one inbox is flagged. Infrastructure
- 4 emails / sequence Sweet spot for most B2B sequences. Top-of-funnel SaaS often uses 6-8; high-trust enterprise uses 3-4. Cadence
Where these benchmarks come from
Twelve years of running outbound across India, APAC, North America, and Australia. The reply-rate and reply-to-meeting numbers are pulled from rolled-up campaign data across B2B SaaS, services, and FinTech. The infrastructure ratios (inboxes-per-day, inboxes-per-domain) are deliverability-team consensus across Smartlead, Apollo, and Lemlist — push them at your own risk.
Frequently Asked Questions
How many inboxes do I need for cold email?
Most teams send 30 emails per inbox per day in steady state (after a 2-3 week warmup). Divide your daily email volume by 30 and round up. The calculator does this for you — change the per-inbox number in Adjust assumptions if your stack tolerates more.
How many domains do I need for cold email?
A safe rule is 3 inboxes per domain. Going higher risks deliverability cascades — if one inbox gets flagged, others on the same domain inherit reputation damage. Total domains = inboxes ÷ 3, rounded up.
What is a realistic reply rate on cold email?
8-12% reply rate per prospect is realistic across a well-targeted, well-written sequence. Below 5% usually points to ICP or messaging issues. Above 15% is exceptional and usually means very tight ICP + strong relevance hooks.
How many emails should a cold sequence have?
3-6 emails per prospect over 20-25 days is the sweet spot for most B2B sequences. Shorter sequences (3) work for tight ICPs where you can be highly relevant fast; longer sequences (6+) are better for considered purchases where multiple touches build familiarity.
What percentage of replies become meetings?
Roughly 25-35% of replies turn into booked meetings — the rest are out-of-office, soft-pass ("not now"), or unqualified responses. The calculator defaults to 25% (conservative). Tight ICP and crisp qualification push this to 35%.
How do I increase reply rate without scaling infrastructure?
Three levers, in order of impact: (1) tighten your ICP so every prospect has a real trigger to respond; (2) rewrite messaging from product-centric to problem-centric; (3) extend sequence length by 1-2 touches. Doing all three on a 1,000-prospect list often outperforms doubling the list with the same messaging.
Why does sequence length change my infrastructure needs?
Because each prospect receives multiple emails. If your sequence is 4 touches and you need 800 prospects, that's 3,200 emails — not 800. Doubling sequence length doubles email volume, which doubles inbox and domain requirements. Most teams under-provision because they forget this multiplier.
Is this calculator only for cold email, or also LinkedIn?
It's calibrated for cold email. LinkedIn outreach has different ratios (lower volume, higher per-touch response rate, no inbox/domain provisioning question). If you're running a multi-channel sequence, count only the email touches when entering sequence length.