How to calculate tonnage when area is given for a/c quickly?

For Office area :14 -16 sq.meter per TON

For Commercial Markets and Malls12 -14 sq.meter per TON

For public assembly area like mosque, Audotorium :10 -12 sq.meter per TON

For Data Center2 -5 : sq.meter per TON

area multiply by .0.08

This is the most horrible scam in HVAC.

1st. : We are cooling volume , not area.

2nd. : We are removing heat load from that volume .

3rd. : We deal with latent heat load and sensible heat load.

4th : Coaling load depends on many parameters (location, altitude, people, lights, equipments, activities, ... etc)

So there is no such quick calculation.

But in every country the contractors (experimentally) developed their (load /volume) estimation for : furnished apartments with shaded windows, not under roof or at the ground floor, without kitchen.

For example : - Middle east : 35:40 m3/Ton

                    - North Africa : 45 : 50 m3/Ton

                    - Euorope : 50 : 55 m3/Ton

But this is not a rule, and it depends only on experimental, and it will vary from contractor to another.

You can use the quick load estimated tables in ASHRAI which is more accurate according to estimated factors ( No. of occupants , glass to wall %, wall material, equipments, lights, occupation time, ..etc)

by verifying the sources of heat gain in a building envolope 

12-14 m2 =1 TON if the height10 ft for more than this load will increase and each ft2 =1.5 to2.4 cfm

Usually we take120 sq ft  area of a room =1 Ton.

 Moath Samara yes u r correct but we have magic number too

Gulf area, in general each12-15 square meter equal1 Ton

In general, one cannot estimate the appropriate values that could be close to the design figures. However, if fed with few essential inputs such as geographic location, application, type of building &  internal loads; we can come up with a high side values. There are various PDFs available titled 'THUMBRULE' that proves a helping hand for beginners, but experience in design helps develop knowledge for initial estmiation.

calculate the area and divide by 14 m2, you will get the tonnage

15 to 18 Square meters a ton in case of centralized chilled water system. 12 to 14 Square meters a ton in case of centralized DX package unit air conditioning system.