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Insulation R-Value Calculator

Heat loss through a wall from R-value and ΔT.

Introduction

Insulation R-Value Calculator — Heat loss through a wall from R-value and ΔT. Enter R-value (imperial, e.g. R-13), Temperature difference (°), Area (m²) to get an instant, accurate result.

Formula

Enter the imperial R-value printed on the insulation (e.g. R-13, R-30). R-value(SI) = imperial R-value × 0.1761 m²·K/W. Heat flux = ΔT / R-value(SI). Total heat loss (W) = flux × area.

Step-by-step

  1. Enter the R-value (imperial, e.g. R-13).
  2. Enter the Temperature difference (°).
  3. Enter the Area (m²).
  4. Click Calculate to see your result instantly.

Real-world example

Example: With R-value (imperial, e.g. R-13) = 13, Temperature difference (°) = 20, Area (m²) = 50, the Insulation R-Value Calculator gives Flux W M2: 8.7358, Total Heat Loss W: 436.7895, R Value Si M2kw: 2.2894.

Frequently Asked Questions

What does a higher R-value mean?
Better insulating performance — less heat passes through for the same temperature difference.
What is ΔT?
The temperature difference between the inside and outside of the insulated surface.
Why enter the R-value printed on the insulation (e.g. R-13, R-30)?
The R-value input is the standard North American imperial R-value (ft²·°F·h/BTU) found on insulation packaging — not a direct RSI (SI) value. The calculator converts it to SI units (RSI, m²·K/W) internally before computing heat flux in W/m², since the temperature and area inputs are metric. If you already have an RSI value, multiply it by 5.678 first to get the equivalent imperial R-value before entering it here.
What inputs does the Insulation R-Value Calculator need?
You'll need to provide: R-value (imperial, e.g. R-13), Temperature difference (°), Area (m²). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Insulation R-Value Calculator?
The Insulation R-Value Calculator applies the formula exactly as calculated — Enter the imperial R-value printed on the insulation (e.g. R-13, R-30). R-value(SI) = imperial R-value × 0.1761 m²·K/W. Heat flux = ΔT / R-value(SI). Total heat loss (W) = flux × area. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Insulation R-Value Calculator free to use?
Yes, the Insulation R-Value Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Insulation R-Value Calculator

The Insulation R-Value Calculator uses a real, verifiable formula — Enter the imperial R-value printed on the insulation (e.g. R-13, R-30). R-value(SI) = imperial R-value × 0.1761 m²·K/W. Heat flux = ΔT / R-value(SI). Total heat loss (W) = flux × area. — so results are accurate every time, not an approximation.