AON vs MRSH: Aon and Marsh & McLennan Companies compared
The short version
From the latest prices and each company's SEC filings. Who's ahead on each measure, not which to buy.
- Marsh & McLennan Companies is the larger company, worth $89.6B, about 1.5 times Aon.
- Marsh & McLennan Companies grew revenue faster over the last year (+6.2% vs +2.2%).
- Aon keeps more of each dollar of revenue as operating profit (26.5% vs 21.6%).
- On earnings, Aon is the cheaper stock (15.3x vs 23.3x).
- Aon's price assumes faster free cash flow growth: about 4% a year, against 4% for Marsh & McLennan Companies (reverse DCF).
Side by side
The stronger figure is shaded where higher (or, for valuation multiples, lower) reads as better. How the implied growth works.
| Measure | AON | MRSH |
|---|---|---|
| Market cap | $59.6B | $89.6B |
| Share price | $273.47 | $175.76 |
| Revenue (last fiscal year) | $17.2B | $27.0B |
| Free cash flow (last fiscal year) | $3.2B | $5.0B |
| Revenue growth, last year | +2.2% | +6.2% |
| Revenue growth per year, last 5 fiscal years | +9.0% | +8.0% |
| Operating margin | 26.5% | 21.6% |
| Net margin | 22.3% | 14.2% |
| Return on equity | 40.8% | 25.8% |
| P/E (trailing) | 15.3x | 23.3x |
| Price / free cash flow | 18.5x | 17.9x |
| EV / EBITDA | 12.1x | 16.2x |
| FCF growth the price implies | 4.0% | 3.6% |
| Dividend yield | 1.1% | 2.0% |
| Debt / equity | 4.55x | 2.87x |
| Fundamental grade | C | C |
| Superinvestors holding it | 13 | 9 |
| Insider purchases, last 12 months | 7 | 8 |
Results from SEC filings
Revenue and free cash flow by fiscal year, from each company's 10-K filings.
Aon
| Year | Revenue | Free cash flow | Op. margin |
|---|---|---|---|
| 2021 | $12.2B | $2.0B | 17.1% |
| 2022 | $12.5B | $3.0B | 29.4% |
| 2023 | $13.4B | $3.2B | 28.3% |
| 2024 | $15.7B | $2.8B | 24.4% |
| 2025 | $17.2B | $3.2B | 25.3% |
Marsh & McLennan Companies
| Year | Revenue | Free cash flow | Op. margin |
|---|---|---|---|
| 2021 | $19.8B | $3.1B | 21.8% |
| 2022 | $20.7B | $3.0B | 20.7% |
| 2023 | $22.7B | $3.8B | 23.2% |
| 2024 | $24.5B | $4.0B | 23.8% |
| 2025 | $27.0B | $5.0B | 23.1% |
Where the revenue comes from
Aon · by segments, 2025
Risk Capital$11.3B66%
Human Capital$5.9B34%
Marsh & McLennan Companies · by segments, 2025
Risk and Insurance Services$17.3B64%
Consulting$9.8B36%
Compare them in fullFifteen years of statements, quarterly results, DCF and IRR models, and any number of peers side by side.
Open AON in InvestinglyQuestions
Which is bigger, Aon or Marsh & McLennan Companies?
Marsh & McLennan Companies (MRSH), at $89.6B against $59.6B.
Is AON or MRSH cheaper?
By trailing P/E, Aon (15.3x) is cheaper than Marsh & McLennan Companies (23.3x). A lower multiple can also mean the market expects less growth.
Which grows faster, AON or MRSH?
Marsh & McLennan Companies: revenue grew +6.2% over the last year, against +2.2%.
Prices and ratios as of the last daily update; statements from SEC filings. Information only, not investment advice.