What Is a Molecular Formula from Empirical Calculator?
An empirical formula shows only the simplest ratio of atoms in a compound — the real molecule can be a whole-number multiple of that ratio. This calculator computes the empirical formula's mass from the atomic masses and subscripts you enter, compares it to the compound's actual (experimentally measured) molar mass, and scales every subscript up by the resulting multiplier n to reconstruct the molecular formula.
This is the standard second step after determining an empirical formula, and it's exactly how chemists confirm compounds like glucose (C6H12O6) from a simpler empirical formula like CH2O.
How to Read Your Results
Molecular Formula
The reconstructed true formula, with every empirical subscript multiplied by n.
Empirical Formula Mass
The molar mass of just the empirical formula, calculated as the sum of (atomic mass × subscript) for each element you entered.
Multiplier (n)
The raw ratio of actual molar mass to empirical formula mass, along with the whole number it rounds to. This whole number should be close to the raw value — a large mismatch suggests an error in your entered data.
Computed Molecular Mass
The empirical formula mass multiplied by the rounded n, shown so you can compare it back against your entered actual molar mass as a sanity check.
Real-World Example
A compound has the empirical formula CH2O (empirical mass ≈ 30.03 g/mol) and an experimentally determined molar mass of about 180.16 g/mol.
| Quantity | Value |
|---|---|
| Empirical formula mass | 30.03 g/mol |
| Actual molar mass | 180.16 g/mol |
| Multiplier (n) | 180.16 ÷ 30.03 ≈ 6 |
| Molecular formula | C6H12O6 (glucose) |
Multiplying each empirical subscript (C1, H2, O1) by 6 gives C6H12O6 — the correct molecular formula for glucose.
Tips for Accurate Results
- Determine the empirical formula first using combustion or elemental analysis data.
- The multiplier n should land very close to a whole number — if it's not (like 5.4), double-check your molar mass or atomic masses.
- Molar mass is often measured by mass spectrometry or, for gases, the ideal gas law (PV = nRT).
- n = 1 means the empirical formula and molecular formula are the same.
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Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team