Email send rate calculator: emails per hour, per minute and the gap between sends
In short: Paces a send across inboxes and a daily window: per inbox per hour, all inboxes per minute, seconds between sends and sending days, against Gmail, Google Workspace, Microsoft 365 and Outlook.com limits. Limit: Provider limits are abuse ceilings, not safe cold email volumes; the per-inbox number is your own.
Send rate is how fast a volume goes out: emails per inbox per day spread across the hours you send. 30 a day from one inbox over an 8-hour window is about 4 an hour, one every 16 minutes. Enter the total, inboxes, daily cap and window to get per-hour and per-minute rates, the gap and the days needed.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. See pricing
Your own number. Cold email platforms suggest 30 to 50 for a warmed inbox.
For example 8 for 9am to 5pm in the recipients' time zone.
Send one email from each inbox every 16 min: 300 a day, done in 20 sending days (about 4 weeks).
- Per inbox per hour
- 3.8
- All inboxes per hour
- 38
- All inboxes per minute
- 0.63
- Gap per inbox
- 16 min
30 a day per inbox × 10 inboxes = 300 a day. Spread over 8 hours, each inbox sends 3.8 an hour, one every 16 min. Most sending tools add a random delay on top, so the real gaps vary around this.
Google Workspace (paid)'s published ceiling is 2,000 a day per mailbox when every recipient is new and external (messages per user per day); 30 is under it. These are abuse ceilings, not safe cold email volumes. Gmail sending limits in Google Workspace
Next step
6,000 emails at 300 a day.
Pacing keeps the receiving servers from throttling you, but every hard bounce in those sends still counts against each inbox. Drop the list here to see which addresses are still live before the first day goes out.
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Sample result
6,000 emails from 10 inboxes at 30 a day: one email per inbox every 16 minutes, done in 20 sending days.
- Gap per inbox
- 16 min
- All inboxes per hour
- 38
- Sending days
- 20
What this means for you
An even pace through the window keeps receiving servers from throttling you.
- Per hour, per minute and the gap
- Days and weeks to finish
- Gmail, Workspace, M365, Outlook.com
- Your own per-inbox number
- Throttling
- Cold email
- Calculator
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
How do I work out emails per hour for a send?
- Enter how many emails to send, how many inboxes send them, and how many each inbox should send a day.
- Set the sending window in hours (for example 8 for 9am to 5pm in the recipients' time zone) and the sending days a week.
- Pick the mailbox provider to check the pace against its published daily and per-minute limits.
- Use the gap between sends as your sending tool's minimum delay, and the days figure to plan the campaign.
Example
- You enter
- 6,000 emails from 10 Google Workspace inboxes at 30 a day each, over an 8-hour window, 5 sending days a week.
- You get
- 300 a day, finished in 20 sending days (4 weeks). Each inbox sends 3.8 an hour, one every 16 minutes; all inboxes together send about 38 an hour, 0.63 a minute. 30 a day is under Workspace's 2,000 a day per user.
- Limits
- Runs in your browser.
How do you calculate emails per hour?
Per inbox per hour = emails per inbox per day ÷ window hours, and the gap between sends = window hours × 3,600 ÷ emails per inbox per day, in seconds. For all inboxes together, multiply by the number of inboxes. 6,000 emails from 10 inboxes at 30 a day is 300 a day and 20 sending days; over an 8-hour window that is 37.5 an hour across all inboxes, each sending one every 16 minutes. In a spreadsheet with per inbox per day in A2 and window hours in B2: =A2/B2 an hour and =B2*3600/A2 seconds apart.
The per-inbox number is yours to choose. No mailbox provider publishes a safe cold volume; cold email platforms' own advice, such as Instantly's, is 30 to 50 a day for a warmed inbox, and the cold email volume calculator works out how many inboxes and domains a daily target needs.
Why send slowly instead of all at once?
Receiving servers limit how fast they accept mail from a sender they don't know well. Send in a burst and they answer with temporary 4xx deferrals, the throttling that slows a campaign down and, repeated, hurts the sender's reputation. Google's sender guidelines ask senders to increase volume slowly and keep it consistent, and an even pace through the day is the simplest way to do that.
The provider limits in the check are abuse ceilings, read from each provider's own page: Google Workspace allows 2,000 unique external recipients a day per user, and Microsoft 365 10,000 recipients a day and 30 messages a minute per mailbox. Being under them is necessary, not sufficient. The sending limits calculator lists every published limit per account.
Same 300 a day, different windows
| Window | All inboxes per hour | Gap per inbox (10 inboxes) |
|---|---|---|
| 4 hours | 75 | 8 minutes |
| 8 hours | 37.5 | 16 minutes |
| 12 hours | 25 | 24 minutes |
Each inbox sends 30 a day. Most sending tools add a random delay on top of the minimum gap.
Who uses this tool, and for what?
- Cold emailers
- Set the minimum delay in Instantly or Smartlead from the inbox count and window, and see how many days the list takes.
- Sales teams
- Pace a one-off announcement from a few Workspace mailboxes without hitting Google's daily limits.
- Developers
- Throttle transactional or batch sends from Microsoft 365 under the 30-a-minute mailbox limit.
What can’t this tool tell you?
- Provider limits are abuse ceilings, not safe cold email volumes; the per-inbox number is your own.
- It assumes an even pace; real sends add random delays and skip days.
- Sending platforms such as Amazon SES set per-account rates that aren't listed here; choose Other for those.
Common questions
- How many emails can I send per hour?
- Gmail and Google Workspace publish daily limits, not hourly ones. Microsoft 365 limits each mailbox to 30 messages a minute and 10,000 recipients a day. For cold email the useful limit is your own per-inbox daily number spread over your sending window, usually a few an hour per inbox.
- How long should the delay between cold emails be?
- Window seconds ÷ emails per inbox per day. 30 a day over 8 hours is one every 16 minutes per inbox. Sending tools usually let you set a minimum delay and add random jitter on top.
- What is email throttling?
- A receiving server limiting how much mail it accepts from you in a period, with temporary 4xx replies so your server retries later. Sudden volume spikes from a sender it doesn't know are the usual trigger.
- Does sending slower help deliverability?
- An even, gradual pace avoids throttling and matches Google's advice to increase volume slowly. It doesn't fix bounces, complaints or authentication, which matter more.
- Is anything sent to a server?
- No. The calculator runs in your browser.
Sources
Authentication and capacity are half of deliverability.
The other half is who you send to. Every hard bounce counts against the domain and inboxes you are sending from, and nothing in DNS can tell you which addresses on your list are dead.
- Bulk verification with real SMTP mailbox checks
- Hard bounces removed before a send, not discovered after
- Catch-all, disposable and role detection on every row
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