Free calculator

Cold email inbox, domain & warmup calculator

To find how many inboxes you need, divide your daily send volume by the cap you set per inbox per day; then divide inboxes by inboxes per domain to get domains. At 10,000 emails a month over 20 sending days and 30 sends per inbox per day, that is 17 inboxes on 6 domains. This planner also prices the setup and lays out a week-by-week warmup ramp with the date you reach full volume.

Your inputs

Every pre-filled number is a default assumption — replace it with your numbers. Defaults are placeholders, not industry benchmarks.

Results

Inboxes needed: 17; 510 sends/day capacity
Domains needed: 6; at 3 inboxes each
Daily send volume: 500; over 20 sending days
Monthly infra cost: $210; $2,520 / yr
Cost per 1,000 emails: $21.00
Full volume from: —

Domains / mo: $6.00
Inboxes / mo: $119
Warmup tool / mo: $85.00

Warmup ramp schedule

Week-by-week maximum daily sends per inbox and across all inboxes
Week	Starts	Per inbox / day	All inboxes / day
1	—	8	136
2	—	15	255
3	—	23	391
4+	—	30	510

Week 4+ is full volume. Ramp is linear — a planning default, not a rule; follow your warmup tool's guidance and slow down if placement drops.

How this is calculated

Capacity

daily volume = ⌈ monthly target ÷ sending days ⌉
inboxes      = ⌈ daily volume ÷ sends per inbox per day ⌉
domains      = ⌈ inboxes ÷ inboxes per domain ⌉

Cost

monthly cost = domains × domain cost per year ÷ 12
             + inboxes × inbox cost per month
             + inboxes × warmup tool per inbox per month
cost per 1,000 emails = monthly cost ÷ (monthly target ÷ 1,000)

Warmup ramp

for week w = 1 … W:  sends per inbox per day = round(C × w ÷ (W + 1))
week W + 1 onward:   sends per inbox per day = C
full-volume date   = start date + W × 7 days

⌈ ⌉ means round up. C is your per-inbox daily cap and W is the number of warmup weeks.

Assumptions & defaults

The pre-filled values are starting assumptions so the calculator shows a result on load. They are not industry statistics — replace each one with your own numbers.

Default target of 10,000 cold emails per month over 20 sending days.
Default cap of 30 sends per inbox per day and 3 inboxes per domain — both are planning assumptions to replace with your own limits.
Default 3-week warmup with a linear ramp; real warmup tools may ramp differently.
Placeholder costs of $12 per domain per year, $7 per inbox per month and $5 per inbox per month for warmup. Use your actual provider pricing.
Inbox count is sized for the target volume only; add spares if you rotate or rest inboxes.
The start date defaults to today in your browser's time zone.

Frequently asked questions

How many inboxes do I need for cold email?

Divide your monthly target by sending days to get daily volume, then divide daily volume by the number of emails you allow each inbox to send per day and round up. For example, 10,000 emails a month over 20 sending days is 500 a day; at 30 per inbox per day that is 17 inboxes.

How many domains do I need?

Divide the number of inboxes by how many inboxes you put on each domain and round up. Seventeen inboxes at three per domain needs six domains. Spreading inboxes across domains limits the damage if one domain's reputation drops.

How long should I warm up new inboxes?

The calculator defaults to three weeks as an editable planning assumption, not a rule. Follow your warmup tool's guidance and your own placement tests, and extend the ramp if inbox placement drops.

How is the warmup ramp schedule built?

It ramps linearly. With W warmup weeks and a daily cap C, week w allows about C × w ÷ (W + 1) sends per inbox per day, and the week after warmup is the first at the full cap. The table also multiplies by inbox count to show total daily volume.

What does the monthly infrastructure cost include?

Domain registration spread over twelve months, the monthly cost of each inbox, and the warmup tool's per-inbox fee. Sending platform, data and copywriting costs are not included.

Is 30 emails per inbox per day a safe limit?

Thirty is only the calculator's default assumption. The right cap depends on your provider, domain age, list quality and engagement, so set it from your own deliverability monitoring rather than from a generic number.