Watts to BTU/hr Calculator
Use this tool to instantly convert electrical power in watts to heat output in BTU per hour (BTU/hr).
Reverse: BTU/hr to Watts
Reference factor used: 1 watt = 3.412141633 BTU/hr.
How to convert watts to BTU/hr
If you are sizing a heater, evaluating appliance heat output, or comparing electrical devices with HVAC ratings, you will often need a watts to BTU conversion. The correct comparison is usually watts to BTU per hour (BTU/hr), because watts and BTU/hr are both rates of energy transfer.
This calculator gives you a quick and accurate conversion for both directions: watts to BTU/hr and BTU/hr to watts.
Watts to BTU formula
Primary formula
BTU/hr = Watts × 3.412141633
Reverse formula
Watts = BTU/hr ÷ 3.412141633
In many practical situations, using 3.41 is accurate enough. For engineering work, use the full factor shown above.
Quick conversion chart
| Watts (W) | BTU/hr | Typical Context |
|---|---|---|
| 100 W | 341.21 BTU/hr | Small electronics or lighting |
| 500 W | 1,706.07 BTU/hr | Compact space heater setting |
| 1,000 W | 3,412.14 BTU/hr | Appliance or medium heater load |
| 1,500 W | 5,118.21 BTU/hr | Common portable space heater |
| 3,500 W | 11,942.50 BTU/hr | Near one ton of cooling equivalent |
| 5,000 W | 17,060.71 BTU/hr | High-load electrical equipment |
Practical examples
Example 1: Electric heater
You have a 1,500 W heater and want to know its heat output:
1,500 × 3.412141633 = 5,118.21 BTU/hr.
Example 2: Small AC rating comparison
You see an air conditioner rated at 12,000 BTU/hr and want a rough watt equivalent:
12,000 ÷ 3.412141633 = 3,516.85 W.
BTU vs BTU/hr: common confusion
A BTU is a unit of energy. A BTU/hr is a unit of power (energy per hour). Since watts are also power, watt-to-BTU comparisons should almost always use BTU/hr. If someone says “BTU” in HVAC conversation, they often mean BTU/hr informally.
Where this conversion is useful
- Comparing electric heaters with furnace or HVAC output ratings
- Estimating heat gain from appliances and lighting in a room
- Converting generator or electrical load values for thermal analysis
- Understanding cooling capacity and electrical demand relationships
Frequently asked questions
How many BTU/hr is 1 watt?
1 watt equals 3.412141633 BTU/hr.
How many watts is 1 BTU/hr?
1 BTU/hr equals approximately 0.293071 watts.
Is this calculator good for HVAC sizing?
It is excellent for unit conversion, but HVAC sizing should also include room size, insulation, windows, occupancy, and climate. Use this conversion as one part of your overall load estimate.
Final note
Whether you are checking appliance heat output, comparing heating systems, or translating HVAC specs, this convert watts to btu calculator gives fast, reliable answers with clear formulas.