Drivers often search for this, so our team has opened this topic for the community. The figures below concern the UK; rules differ by country.
In the UK, there has been a drug-driving limit for THC since 2015: 2 micrograms per litre of blood. CBD itself is not limited. The issue is that CBD products can contain THC, and it is THC that the law targets.
Elsewhere the rules can be much stricter. In France, for example, any detected amount of THC is an offence, whatever the quantity.
This is not legal advice. Please check official sources in your country, and never drive if you feel impaired.
Do you check the THC content of your CBD products because you drive? For readers outside the UK, how does it work where you live?