Depends on stack sizes, and the nature of our hand and our opponent's likely holdings.

If the $10 puts you all in, it's pot odds. If you have $5 behind, you need 20% equity. If you have $10, you need 28.5% equity.

As stack sizes increase, the river action becomes more important - i.e. implied odds and the odds of someone getting bluffed off their hand.

If, on the river, you know whose hand is best and how your opponent will react, then you make much more money than otherwise. You can bluff him off his weak hands that beat you, you can extract the maximum when you have a strong hand, and you can fold when you're beat. Therefore the more we know this, the more +EV the river is, and the less equity we need on the turn. Conversely the more the opponent knows, the more -EV the river is, and the more equity we need on the turn.

If we have no made hand but are drawing to the nuts or near-nuts (e.g. nut flush draw on unpaired board), then we will almost always know if our hand is good or not, because on the river its value usually polarises to nuts or air. This means we don't get bluffed, don't get value towned, and don't miss value bets.

If we have a more marginal hand like TPGK, we have difficult decisions on the river. We'll sometimes have to fold the best hand when draws complete, we'll probably pay off TPTK+ hands, and we don't get value from much (missed draws will bluff or fold).

If we know our opponent's likely holdings and tendencies, this also helps. If we somehow know that our opponent has the nut flush vs our bottom set, and stacks are deep, you can play the river perfectly and so calling is +EV with only ~23% equity.

If your opponent's range is more balanced and you don't have reads, when he bets pot on the river you're sometimes going to get bluffed or pay off big hands, and when he checks you'll sometimes miss value or get checkraised.

So you need ~29% equity, but:

• Less if you're very short stacked

• Less if you're drawing to the nuts, more if you have a marginal hand

• Less if you can put your opponent on a narrow range, more if his range is balanced

• Less if your hand is face-up, more if it's disguised

• Less if your opponent is bad/exploitable, more if you're the one being outplayed