BET Surface Area Calculator

Analyze multipoint adsorption data with linear regression. Customize molecular area and standard volume. View Vm, C, R², and surface area in seconds accurately today.

Enter adsorption data (P/P0 and v) to estimate surface area.

Input Data

Common default for nitrogen: 0.162 nm².
Approximate value: 22414 cm³/mol.
Default is the SI exact constant.

BET Points (Relative pressure and volume)

P/P0 (x) Adsorbed volume v (cm³ STP/g) BET y = x / (v(1-x))
0.004279
0.005612
0.007087
0.008711
0.010684

Tip: The BET method is usually applied in a limited linear region (often x ≈ 0.05–0.30). Use data points from the linear range for best results.

Formula Used

The linear BET form uses relative pressure x = P/P0 and adsorbed volume v (at STP):

y = x / ( v (1 − x) )

A straight-line fit gives y = m x + b. From the slope (m) and intercept (b):

  • Vm = 1 / (m + b) (monolayer capacity, cm³ STP/g)
  • C = 1 + m/b (BET constant)

Specific surface area is computed using molecular cross-sectional area σ:

S = (Vm / Vmolar) · NA · σ · 10⁻¹⁸   (m²/g)

Here, Vmolar is molar volume at STP (cm³/mol), and σ is in nm²/molecule.

How to Use This Calculator

  1. Enter the molecular cross-sectional area and STP molar volume.
  2. Add at least three adsorption points (x and v).
  3. Keep x strictly between 0 and 1.
  4. Prefer the linear BET range for your material.
  5. Press Calculate to see results above the form.
  6. Download CSV or PDF for reports and records.

Example Data Table

Sample values below demonstrate a typical low-pressure BET region. Replace them with your measured isotherm points for meaningful results.

P/P0 (x) v (cm³ STP/g) y = x/(v(1-x))
0.05 12.3 0.004279
0.1 19.8 0.005612
0.15 24.9 0.007087
0.2 28.7 0.008711
0.25 31.2 0.010684

Accurate BET calculations help compare porous materials reliably worldwide.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.