The math, in plain words
Cold email is a funnel with four leaks. Contacts reply. Some replies are positive. Some positive replies book. Some booked meetings show up. Multiply the four rates and you get meetings per contact. Divide your goal by that number and you get the contacts you need.
From there the sending side is simple. Contacts times sequence steps gives emails. Emails divided by what one inbox can safely send in a month gives inboxes. Inboxes divided by how many you put on each domain gives domains.
Two simplifications. Some contacts reply early and skip later steps, so real email counts run a little lower. And you will lose a few contacts to bad data, so source about 10% more than the calculator says.
What reply rate should you plan for?
| Benchmark | Reply rate | Source |
|---|---|---|
| Platform average | 3.43% | Instantly benchmark report 2026 |
| Top quartile | 5.5%+ | Instantly benchmark report 2026 |
| Elite campaigns | 10%+ | Instantly benchmark report 2026 |
| One Zero active clients | 9.4% | Our average across active campaigns |
Plan with the average if you are starting from scratch. Most first campaigns land there. Plan with the top quartile only if you have a proven offer and a tight list. The gap between them is mostly copy and targeting, which is the cheapest part of the stack to fix.
Which number to fix first
Look at the "Biggest lever" panel above. It shows how many fewer contacts you would need if you improved each rate a little. Nine times out of ten, reply rate wins, because it sits at the top of the funnel and every later step multiplies it.
- Reply rate moves with the offer, the list and the first line. Read how to write a cold email.
- Positive share moves with targeting. If most replies say "not relevant", your list is wrong, not your copy.
- Booking rate moves with reply speed. Answer within an hour and offer two times, not a calendar link alone.
- Show rate moves with a confirmation email and a reminder the morning of the call.
Questions people ask
How many cold emails do I need to send to get one meeting?
At a 3.4% reply rate, 30% of replies positive, 60% booked and 80% showing up, you need about 200 contacts per held meeting. With a 4 step sequence that is roughly 800 emails. Better copy and targeting can cut that by more than half.
How many emails can one inbox send a day?
We keep cold sending around 30 a day per inbox, plus warmup. If you need more volume, add inboxes and domains instead of pushing one inbox harder.
How many inboxes should I put on one domain?
We usually run 2 to 3 per domain. More than that and one bad week can drag every inbox on the domain down together.
Should I count opens?
No. Apple Mail and privacy tools fire opens automatically, so open rate tells you very little. Count replies and meetings. Here is why open rates stopped meaning much.
Benchmarks: Instantly Cold Email Benchmark Report 2026, based on platform data from 2025.