How to convert void ratio to porosity
Porosity asks what fraction of the total sample volume is voids. It uses a different denominator from void ratio, even though both describe the same sample.
What the formula is saying
Imagine one unit of solids. A void ratio e gives e units of voids, so total volume is 1 + e. The void fraction is therefore n = e/(1+e).
Read the symbols in plain language
- e
- Void ratioratio / no unit
Sort out the units first
Enter e as a ratio, for example 0.5, not 50. The intermediate n = e/(1+e) is a fraction; the final result is n × 100 percent.
Let’s solve one together
Read the given values, follow each operation, then check what the result means.
- e · Void ratio
- 0.5
Build total volume relative to one unit of solids
One unit of solids plus e units of voids gives the denominator.
1 + (0.5) = 1.5Divide voids by total volume
This changes the reference from solids to the complete sample.
(0.5) ÷ (1.5) ≈ 0.3333333333Convert the fraction to percent
The formula engine reports percent. Keep the fraction for equations that expect n between 0 and 1.
(0.3333333333) × 100 ≈ 33.33333333 %
Does this worked answer make sense?
Convert the percentage back to a fraction before checking e = n/(1−n). Keep the unrounded fraction for this reverse calculation.
Now try your own values
Change a value or its unit. The same method will show your calculation, step by step.
Results update only when you calculate. The lesson example above stays unchanged.
Your turn — check your understanding
Use these new values. Work it out first, then check your answer.
- e · Void ratio
- 0.8
Find: void ratio to porosity
A hint, not the answer
Imagine one unit of solids. A void ratio e gives e units of voids, so total volume is 1 + e. The void fraction is therefore n = e/(1+e).
Enter e as a ratio, for example 0.5, not 50. The intermediate n = e/(1+e) is a fraction; the final result is n × 100 percent.
Show the full practice solution
Compare the steps with your work; revealing a solution does not mark the lesson complete.
Build total volume relative to one unit of solids
One unit of solids plus e units of voids gives the denominator.
1 + (0.8) = 1.8Divide voids by total volume
This changes the reference from solids to the complete sample.
(0.8) ÷ (1.8) ≈ 0.4444444444Convert the fraction to percent
The formula engine reports percent. Keep the fraction for equations that expect n between 0 and 1.
(0.4444444444) × 100 ≈ 44.44444444 %
Avoid the common trap
Porosity and void ratio are not interchangeable. A void ratio of 0.5 corresponds to about 33.333% porosity, not 50%.
When this method applies — and when it does not
Nonnegative finite void ratio and positive solid volume. For a sample with solids, the porosity fraction is less than 1 and its percentage is less than 100%.
For study and understanding, not approval of a real structure, site operation or design. Apply the correct standard, National Annex and professional review to actual engineering work.
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Sources & further reading
References open in a new tab and explain the underlying principles. The teaching text and examples here are SimpleFlick’s own; the source organisations have not endorsed this calculator.
Lesson updated: · Worked examples checked against the implemented formula; not an independent engineering certification.