Tire load can pertain to two different definitions or numbers. A tire’s load rating, usually expressed as an alpha or alpha-numeric value defines how much total weight that tire is able to support, when properly mounted and inflated. Whether your tires uses an alpha or an alpha-numeric load rating depends on whether you have passenger car tires or light truck tires. Your tires’ load rating can be read on the sidewall and then referenced on these light truck and car charts. To determine actual load, you need to have your car weighed and compensate for weight distribution, which in most vehicles is 70-30 front to rear.
For more info, see 3 Tire Care Secrets of the Pros