Mg/ml is only half the story. How a vape feels depends on the device too. A higher-wattage device will vaporize more liquid per puff, so you get more nicotine per hit even at the same mg/ml. That's why a 10 mg/ml in a powerful mod can hit harder than a 20 mg/ml in a small disposable. If you're switching between device types, adjust your strength accordingly.

Also, check the label for 'nicotine by volume'—that's just another way of saying mg/ml. Some brands use one term, some use the other. Now you know they're the same thing.