The size or capacity of your Air Conditioner is determined by the amount of Btu (British thermal unit) and the Tonnage (12.000 Btu = 1 Ton). What amount of Btu and Tonnage should your AC have in order to cool your home or office? At AL Naveed AC System Installation LLC, we use a complex formula and factor in many details to determine the exact amount of Btu your new air conditioner should have, we provide you with this free online Btu and Tonnage calculator (also known as load calculation) to give you a estimate. Just fill in your home or office square footage, the number of occupants and windows in the form below.