Void Volume Calculator

Inputs

Choose a method, enter values, then calculate.

All volumes assume 1 cm³ = 1 mL.

Calculation Method *

Pick the model that matches how your data is measured.

Flow rate *

Flow unit

Dead time (t₀) *

Time unit

Column inner diameter *

Diameter unit

Column length *

Length unit

Porosity (ε) *

Porosity unit

Total volume (Vt) *

Volume unit

Solid mass (m) *

Mass unit

True density (ρ) *

Density unit

Include intraparticle pore volume (optional)

Use this if you have pore volume per mass from adsorption or supplier data.

Pore volume per mass (pv)

pv unit

Reset

Example Data Table

These examples demonstrate typical inputs and outputs across methods.

Scenario	Inputs	Output
Chromatography	Flow = 1.2 mL/min, t₀ = 1.85 min	V0 = 2.22 mL
Geometry + Porosity	Diameter = 2.1 cm, Length = 10 cm, ε = 0.38	Vt ≈ 34.64 mL, Vv ≈ 13.16 mL
Total − Solid	Vt = 50 mL, m = 80 g, ρ = 2.5 g/mL	Vs = 32 mL, Vv = 18 mL, ε ≈ 0.36

Formula Used

Chromatography hold-up volume: V0 = F × t0, where F is volumetric flow rate and t0 is dead time.
Cylindrical bed volume: Vt = πr²L, where r = d/2 and L is column length.
Packed-bed void volume: Vv = ε × Vt, where ε is porosity (void fraction).
From mass and density: Vs = m/ρ, then Vv = Vt − Vs. Optionally add Vp = pv × m for intraparticle pores.

Tip: keep units consistent, then convert to your preferred display unit.

How to Use This Calculator

Select the method that matches your experiment or column data.
Enter values and pick units for each field.
Click “Calculate Void Volume” to see results above the form.
Use the download buttons to save a CSV or PDF report.
Use “Reset” to start a new calculation quickly.

FAQs

1) What is void volume in chemistry?

Void volume is the volume not occupied by solid material. In chromatography and packed beds, it represents space available for mobile phase flow and dispersion.

2) What is the difference between V0 and Vv?

V0 is often the hold-up volume from dead time and flow rate in chromatography. Vv is the geometric or calculated void volume in a packed bed, based on porosity and total volume.

3) How do I choose the right method?

Use flow × dead time when you measure t0 using an unretained tracer. Use geometry + porosity for known column dimensions. Use total − solid when you know total volume, packing mass, and true density.

4) Why can porosity be entered as percent or fraction?

Porosity is dimensionless. Some labs report ε as 0.38, while others report 38%. The calculator converts percent to fraction so formulas stay consistent.

5) What does “true density” mean here?

True density is the density of the solid material itself, excluding interparticle voids. It is commonly measured by helium pycnometry or provided by the material supplier.

6) When should I include intraparticle pore volume?

Include it when you have pore volume per mass from adsorption data or supplier specs and you want total accessible void space. For purely flow-through void estimates, keep it unchecked.

7) Why might the calculator warn about negative void volume?

Negative void volume occurs when the computed solid volume exceeds total volume. This usually indicates inconsistent units, an overestimated mass, or a density value in the wrong unit.

8) Are cm³ and mL always interchangeable?

They are equal by definition, but only for volume units. This calculator treats cm³ and mL as identical. Be careful not to mix linear dimensions with cubic units without conversion.

Downloads

After a successful calculation, you can download the latest report:

Download CSV Download PDF

If downloads say “no recent calculation,” compute once first.