Operating Income

Operating income comes from the upper-middle of the income statement. Start with revenue, subtract COGS to get gross profit, then subtract operating expenses — SG&A, R&D, marketing, and depreciation/amortization tied to operations. The result is operating income, the profit from running the core business. It deliberately excludes interest expense (a financing cost) and taxes, so it answers the question 'how profitable is the business itself, regardless of how it's funded?' This makes it more comparable across companies than net income, which is distorted by differing capital structures and tax jurisdictions.

In most cases operating income and EBIT are used interchangeably, and many companies report them as the same number. The subtle distinction: operating income is strictly profit from OPERATING activities, while EBIT (Earnings Before Interest and Taxes) is technically pre-tax income with interest added back — which can include NON-operating items like interest income, investment gains, or one-time asset sale gains. So if a company has meaningful non-operating income, EBIT can be slightly higher than reported operating income. For interview purposes, treat them as the same unless specifically asked about the nuance.

This is the difference interviewers test constantly: the only gap between operating income and EBITDA is depreciation and amortization. Operating income is calculated AFTER subtracting D&A; EBITDA adds D&A back. So EBITDA = Operating Income + D&A. For a capital-intensive business with large depreciation, the gap is huge — operating income may be a fraction of EBITDA. For an asset-light services firm, the two are close. Bankers favor EBITDA for cross-company comparison because depreciation policies vary, but operating income is more conservative because it acknowledges that assets wear out and must be replaced.

Operating margin (Operating Income / Revenue) is one of the most-watched profitability metrics in a comparable companies analysis because it reflects management's efficiency at the operating level, neutral to financing and taxes. Improving operating margin over time signals operating leverage — revenue growing faster than fixed costs. Operating income is also the foundation for unlevered cash flow in a DCF: you typically start with EBIT, tax-affect it to get NOPAT, then add back D&A and adjust for CapEx and working capital. So mastering operating income is a prerequisite for valuation work.