🏠 Home & DIY

Space Heater Size Calculator

Estimate the heater wattage needed to warm a room.

ft²
ft

Results

Heater wattage
2,000 W
BTU/h equivalent
6,824 BTU/h

📊 Space Heater Size Calculator chart

How the heater wattage changes as the room area varies. The orange dot marks your current value.

What is the Space Heater Size Calculator?

Estimate the heater wattage needed to warm a room. Order the right amount the first time. These construction and DIY calculators estimate materials for common home projects and include sensible waste allowances.

Space Heater Size Calculator – free online home & diy tool illustration
Space Heater Size Calculator — free, exact and private.

How to use the Space Heater Size Calculator

  1. Enter your room area, your ceiling height.
  2. Results update automatically as you type; you can also press Calculate.
  3. Read the output: heater wattage, btu/h equivalent.
  4. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Rule of thumb: 10 W per ft² at 8 ft ceilings

Worked example

With room area = 200 ft², ceiling height = 8 ft, the Space Heater Size Calculator returns heater wattage: 2,000 W; btu/h equivalent: 6,824 BTU/h.

Tips for better results

  • Add 5–15% for waste, cuts and breakage depending on the material.
  • Measure twice and round up when buying — returns are easier than second trips.
  • Coverage figures vary by product, so check the label or spec sheet.

⚠️ Material estimates are approximate. Follow local building codes and manufacturer instructions.

Frequently asked questions

What does the Space Heater Size Calculator do?

Estimate the heater wattage needed to warm a room.

How is it calculated?

The Space Heater Size Calculator uses this method: Rule of thumb: 10 W per ft² at 8 ft ceilings.

Can you show an example?

With room area = 200 ft², ceiling height = 8 ft, the Space Heater Size Calculator returns heater wattage: 2,000 W; btu/h equivalent: 6,824 BTU/h.

Is the Space Heater Size Calculator accurate?

It uses standard published formulas and is tested against known values, but results are estimates for guidance. Material estimates are approximate. Follow local building codes and manufacturer instructions.

Is this tool free and private?

Yes — the Space Heater Size Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.

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