The formula
required equity = call ÷ (pot before bet + opponent bet + your call)
If the pot is $100, an opponent bets $50 and it costs you $50 to call, you are risking $50 to contest a final $200 pot. The break-even equity is 25% before considering future betting, rake or realization issues.
Pot odds are not the whole decision
A hand can have enough raw equity but still realize that equity poorly because of position, future betting or dominated outs. Tournament considerations and rake can also matter. Use pot odds as one input, not an automatic call button.