The question usually arrives backwards: «I have five accounts, how many leads will that be?» The useful direction runs the other way — from the result you need to the resources it takes.
Counting backwards
- Leads needed per month.
- Divide by dialogue-to-lead conversion — that gives dialogues needed.
- Divide by comment-to-dialogue conversion — that gives comments needed.
- Divide by one account's daily allowance and by the number of days — that gives accounts.
All conversion rates are yours, from your own data. If you have none, the first month of work is how you get them, on one or two accounts.
Two corrections
Warm-up. An account does not reach its full allowance immediately. If you need volume next month, the accounts are bought today.
Attrition. Part of the fleet will not survive the period. Build in slack: a fleet sized exactly right delivers the target only in week one.
Why more is not always better
Account count runs into venue count. If your niche has a hundred channels, ten accounts will be commenting in the same discussions and the audience starts seeing repeats. The fleet has to grow together with the channel base, not separately from it.
If the calculation says thirty accounts, stop and look at the base first. Thirty accounts across a hundred venues means several of your comments under every post — readers and admins both notice. The right move then is widening the base with the parser, not the fleet.