How many pints of real ale can you drink before you are over the legal driving limit?

None (in countries have a zero tolerance limit)

Depending on where (the legal blood alcohol limit), the ale drunk (it's alcohol content), and your body size, from a fraction of one to maybe slightly more than one.

One 568ml pint of ale at 6% alcohol has 34ml alcohol. A fairly large guy has 5000 mililiters of blood. and so one of those pints gives him almost 0.07% BAC

Here is a list of Blood Alcohol Concentrations allowed for drivers by percent and country:

Zero:

Czech Republic

Slovakia

Romania

Russia

Oman

Brunei

Fiji

Saudi Arabia

United Arab Emirates

Brazil

Bangladesh

Pakistan

Hungary

Canada

0.02%

China

Estonia

Poland

Norway

Netherlands (new licence holders)

Sweden

Puerto Rico

0.03%

India

Serbia

Japan

Uruguay (Zero for truck/taxi/bus drivers)

0.04%

Lithuania (0.02% for drivers in their first two years after gaining a driving license)

Canada: Saskatchewan

0.05%

Argentina (0.02% for motorbikes, 0.00% for truck/taxi/bus drivers)

Australia (0.00% for Australian Capital Territory learner, probationary & convicted DUI drivers, 0.02% for truck/bus/taxi, 0.00% for learner drivers, provisional/probationary drivers (regardless of age), truck and bus drivers, driving instructors and DUI drivers in all other states)

Austria

Belarus

Belgium

Bulgaria

Canada: British Columbia, Ontario, Manitoba, Newfoundland, Nova Scotia, New Brunswick - provincial offence

Costa Rica

Croatia

Denmark

Finland

France (0.025% for bus drivers)

Germany (0.00% for learner drivers, all drivers 18-21 and newly licensed drivers of any age for first two years of licence)

Greece

Hong Kong

Iceland

Ireland (0.02% for learner drivers and professional drivers)

Israel (240μg/L of air. 50μg/L of air for drivers under 24 and professional drivers)

Italy (0.00% for drivers in their first three years after gaining a driving license)

Latvia (0.02% for drivers in their first two years after gaining a driving license)

Luxembourg

Macedonia (0.00% for drivers in their first two years after gaining a driving license)

Netherlands (0.02% for drivers in their first five years after gaining a driving license)

Peru

Philippines

Portugal

Slovenia (0.00% for drivers in their first two years after gaining a drivers licence, drivers under 21 and common drivers, such as buses, trucks...)

South Africa

Spain (0.03% for drivers in their first two years after gaining a driving license and common carriers, such as buses, trucks...)

Switzerland

Thailand

Taiwan

Turkey

0.08%

Canada - criminal offence

Malaysia

Malta

Mexico

New Zealand (0.03% for drivers under 20)

Norway

Puerto Rico (for drivers 21 years and older)

Singapore

United Kingdom

United States