OK, let's see... You have 2 ounces of matter and antimatter, that's about 57 grams or 0.057kg, and the speed of light is 300 million meters per second... thus using E=m*c^2, the energy produced in the detonation is 5.7*10^-2kg * (3.00*10^8m/s)^2 = 5.1*10^15 kg*m^2/s^2, or 5.1 quadrillion (the American kind, a thousand million million) joules. What that is in kT I don't know, but I'll try looking it up...
edit: OK, a "ton of TNT", according to Wikipedia, is defined as 1 gigacalorie, which equals 4.184 billion (thousand million) joules (it also happens to equal a million dietary calories - think of THAT next time you sit down to dinner, since there are a million grams in a metric ton, you are eating the energy equivalent of hundreds of grams of TNT!
Don't let your food a splode!
)... anyway, since the antimatter explosion produces 5.1 quadrillion joules and a ton of TNT is 4.184 billion, that means that the antimatter explosion is equivalent to... 1.2 *billion* tons of TNT (1,200,000 kT) - which is about 10 times more powerful than any bomb mankind has ever devised!
(The most powerful bomb was developed by the Russians during the Cold War and it had an estimated output of 100,000 to 150,000 kT...)
(SJ or some other mathematically inclined person, could you stop by and make sure I didn't horribly screw up the math?
)