The current rules for electing the next Pope require that the Pope-elect receive two-thirds of the votes of the total number of Cardinal electors present for the vote — not two-thirds plus one. If two-thirds is not a whole number, then the number must be rounded up to the next higher whole number. But the general rule is not “two-thirds plus one”, as many persons are now claiming.

For example, if all 117 Cardinal-electors attend the conclave, 2/3rds is 78 votes, a whole number. So only 78 votes would be needed, not 79. If 116 Cardinal-electors are present, then 78 votes are still needed, because 2/3rds would be 77-point-something, and we would then round up to 78 to obtain a whole number. If 115 Cardinal-electors are present, then 77 votes are needed, because 2/3rds would be 76-point-something. At 114 electors, only 76 votes are needed.

So in some cases, we must round up to the nearest whole number, but we don’t add one vote.

— Ronald L. Conte Jr.