" In Sichuan province, 25,493 contact persons were named, 25,347 (99%) were found, 23,178 have already been examined and 0.9% of them were infected. In the province of Guangdong, 9,939 contacts were named, all found, 7,765 are already examined and 4.8% of them were infected. That means: If you have direct personal contact with an infected person, the probability of infection is between 1% and 5%. "

https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf?fbclid=IwAR1r1hTkCcLUPPeXvYXpDkZ4XsuAvUdH1JQFbfE9LztHs0VIH7o3bY6GlWs

This medium post provides a pretty good answer for this question: https://medium.com/swlh/so-youre-going-outside-a-physics-based-coronavirus-infection-risk-estimator-for-leaving-the-house-d7dcae2746c0

And see also the related calculator: https://sygo.mardillu.com/

Answer depends on several things

1. Where you met, temperature, humidity, degree of ventilation

2. Distance and intensity of interaction and exchange of fomites

3. Degree of infectivity (were they coughing and their viral shedding; where they are in illness course)

4. Hygiene, theirs and yours, including hygienic behaviors

5. Your level of immunity (are you already immune, are you immunocompromised, etc)