BTU Calculator
Find the right AC tonnage for your room based on area, climate, and sun exposure
Room Dimensions
Unit
Length
L
Width
W
Ceiling Height (optional)
h
Climate
Sun Exposure
Number of Regular Occupants
ppl
Recommended BTU
—
Tonnage: —
Power (kW)—
Room Area—
Room Volume—
AC Tonnage Guide (India)
1 ton (12,000 BTU) → up to ~120 sq ft
1.5 ton (18,000 BTU) → 120–200 sq ft
2 ton (24,000 BTU) → 200–300 sq ft
How AC Tonnage Is Calculated
BTU (British Thermal Units per hour) measures cooling capacity. 1 ton of AC = 12,000 BTU/hr. The basic rule of thumb is 25 BTU per sq ft of floor area, adjusted for climate, sun exposure, ceiling height, and occupancy. A sunnier, hotter room needs more BTU; a shaded room needs less.
In India's hot climate (especially in May–June), sizing up slightly is common practice. However, over-sizing causes short-cycling — the AC cools too fast, doesn't run long enough to dehumidify properly, and wastes energy.
lightbulb Example
Bedroom: 12×10 ft, sunny, Delhi summer:
1Base: 120 sq ft × 25 BTU = 3,000 BTU
2Hot climate ×1.15 = 3,450; sunny ×1.1 = 3,795
✓ ≈ 4,000 BTU → 1 ton AC is sufficient
quizFrequently Asked Questions
How many BTUs do I need per square foot?
A general rule is 20 BTU per sq ft for standard ceiling heights and insulation. Adjust up for sunny rooms, high ceilings, or poor insulation; adjust down for shaded or well-insulated spaces. A 200 sq ft room needs ~4,000 BTU; 500 sq ft needs ~10,000 BTU. In India's tropical climate, many rooms need 20–25% more cooling capacity.
What is the difference between BTU and Ton of refrigeration?
1 Ton of refrigeration = 12,000 BTU per hour. So a 1.5-ton AC = 18,000 BTU/hr. Indian AC ratings use tons; US and global specs use BTU/hr. Knowing the conversion helps compare AC specifications across brands and markets when selecting cooling equipment.
Does an oversized AC cool a room faster?
Not necessarily — and it's actually harmful. An oversized AC cools the air quickly but shuts off before it can dehumidify properly, leaving the room feeling cold but damp ("short cycling"). The right size cycles properly, maintains temperature and humidity, and uses energy efficiently. Always match BTU rating to room size.