How these are worked out
Each matchup deals every pairing of the two hands that shares no card, then counts all 1,712,304 five-card boards for each. Nothing is sampled, so the figures are exact. A pair against a bigger pair is about 4 to 1 behind; two overcards against a smaller pair is close to a coin flip; a hand that shares a rank with a stronger one, like offsuit ace-king against aces, holds about 7%.
For your own cards against a hand or a range, use the poker odds calculator, or the range equity calculator for one range against another.