Combustion Analysis Calculator
Enter the original sample mass and the masses of CO2 and H2O produced when it was fully combusted. Assuming the sample contains only carbon, hydrogen, and oxygen, the calculator estimates the mass and percentage of each element.
Last updated: September 26, 2026
Frequently asked questions
How does combustion analysis work?
A sample is fully combusted, converting its carbon to CO2 and its hydrogen to H2O. Measuring the masses of CO2 and H2O produced lets you calculate how much carbon and hydrogen were in the original sample.
How is oxygen calculated?
If the sample is assumed to contain only carbon, hydrogen, and oxygen, oxygen mass is found by subtracting the carbon and hydrogen mass from the total sample mass. This only works if no other elements are present.
What if my sample contains nitrogen or sulfur?
The carbon-hydrogen-oxygen-only assumption breaks down, and the 'oxygen by difference' number will actually include the mass of any other elements. Choose the carbon-and-hydrogen-only option instead, or use a different analytical method that can detect the other elements.
Why might the calculator reject my numbers?
If the carbon and hydrogen mass implied by your CO2 and H2O measurements is larger than the whole sample, something is inconsistent, such as a units mismatch or a data-entry error.
Does this replace laboratory elemental analysis?
No. It performs the arithmetic on measurements you already have. It doesn't tell you how to run a combustion experiment or interpret instrument-specific data.
How is this different from the Empirical Formula Calculator?
The Empirical Formula Calculator starts from element percentages you already know. This tool derives carbon and hydrogen content directly from combustion product masses, which is how those percentages are often first measured.