I know this thread is a little old but I thought the question has still been left unanswered. Tonnage is assumed. But, CFM and BTUs are exact.
If anybody wants to know the true size of their a/c or heating system you need to go where the engineers go.
Consumers and contractors need to rethink their thinking when it comes to whole house heating and cooling... (Im from a hot humid area in the USA) Hot dry areas have other needs I won't.
ie... an air conditioner is no longer BTU's in a box. They have evolved into computers. computers that drive the blower motors, the expansion valves, the thermostat/controller can tell you the sub cooling, superheat, and the delta-t. Some tell you if the duct work is incorrect, static pressure against the blower. They are also not as forgiving if installed incorrectly.
Our industry is just catching on, but the consumer is untrustworthy when it comes to duct work and static pressure.
And in our high humidity market having high airflow with low static pressures removes far more humidity then a duct system installed over 10 years ago, Also, most homes lack proper return grille sizes, when the homeowner's desires are to put MERV 16 filters.
Here is a very useful link for duct and grille sizing.
Carry on my friends,
P.S. a neat little read,