Switch models, units, and fluids to match your porous sample today easily. Instantly compute micro to nano scales, then save results as files securely.
Pore-size estimation often relies on capillarity. A curved meniscus across a cylindrical pore creates a pressure jump described by the Laplace relation.
Here, γ is surface tension (N/m), θ is contact angle (deg), and ΔP is pressure difference (Pa). Signs follow cos(θ).
Example using bubble-point mode with water/air (γ ≈ 0.0728 N/m, θ ≈ 0°). Results show how larger ΔP corresponds to smaller pores.
| ΔP (kPa) | γ (N/m) | θ (deg) | Computed diameter d (µm) |
|---|---|---|---|
| 25 | 0.07280 | 0 | 11.6480 |
| 50 | 0.07280 | 0 | 5.82400 |
| 100 | 0.07280 | 0 | 2.91200 |
| 200 | 0.07280 | 0 | 1.45600 |
Pore size quantifies voids that govern flow, diffusion, and capillary action in porous materials. Most tests report an effective diameter or radius inferred from a model, not an exact microscopic shape. Because pores are irregular and connected, one value usually summarizes a distribution. In membranes, you may also see a mean-flow pore size metric.
Bubble-point and intrusion methods relate a pressure difference to an equivalent pore throat. The Young–Laplace relation links the curved meniscus to pressure. Under a cylindrical-throat assumption, smaller pores require higher ΔP to advance the interface.
Surface tension sets the energetic cost of interface area, while contact angle captures wetting on the solid. The factor cos(θ) scales capillary pressure: wetting liquids (small θ) produce larger cos(θ) and stronger capillarity. If θ > 90°, cos(θ) becomes negative, indicating non-wetting behavior in the model.
Bubble-point commonly estimates the largest connected pore that opens first, useful for integrity and leak risk. Intrusion-style calculations across many pressures can outline an apparent size distribution. Always state whether you report diameter or radius, and the exact threshold definition used. Pair results with permeability or porometry data when available.
Calculations use SI internally: γ in N/m and ΔP in Pa, yielding size in meters. Instruments often read kPa, bar, or psi, while results are reported in µm or nm. Converting carefully prevents common 10×–1000× scaling mistakes and mismatched significant figures.
Real structures include tortuosity, ink-bottle pores, and rough surfaces that trap menisci. Temperature, dissolved gases, and contamination change γ and θ. Extra pressure drops from flow resistance, compressibility, or trapped air can bias inferred sizes if not controlled.
Size scales linearly with γ and cos(θ), and inversely with ΔP, so calibration and wetting assumptions dominate uncertainty. A practical check is to vary θ by ±5–10° and compare outputs. Repeated runs and reporting ranges are more honest than extra decimal places.
Use a clean test liquid, control temperature, and record the source of γ and θ values. Increase pressure smoothly, note the onset point carefully, and avoid shocks that alter the sample. For membranes, report the fluid pair and whether the metric is first-bubble, steady bubbling, or breakthrough.
Use capillary intrusion when you know ΔP across a wetting interface. Use bubble-point when gas first penetrates a wetted sample and you want the largest connected pore.
Start with literature values for your material–liquid pair, then treat θ as uncertainty. Measuring θ directly or comparing multiple liquids improves confidence in the inferred size.
Smaller pores force a more curved meniscus. Greater curvature requires higher capillary pressure, so ΔP must rise to push the interface through the throat.
Yes. Select your unit; the calculator converts internally. Ensure your gauge reading reflects the pressure difference across the sample, not additional upstream losses.
One calculation gives an equivalent size at one pressure. To estimate a distribution, compute sizes across many pressures and interpret them using your method’s thresholds and assumptions.
Report the largest pore (bubble-point) for integrity, plus a characteristic or percentile size for performance. Follow the convention in your standard or customer specification.
Surface tension usually decreases as temperature rises, changing the inferred size at fixed ΔP. If temperature varies, update γ (and possibly θ) and document the condition.
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.