How to analyze a P&L, line by line: profit and loss analysis with a worked example

Profit and loss analysis takes three steps: put every line as a percentage of revenue, compare every line with last year, then build a bridge that explains the change in operating profit by cause. On the P&L below, revenue grew 10% to $46,200,000 and net income stayed at $3,330,000. The bridge shows why: a one-point fall in gross margin absorbed $462,000 of the $504,000 that the extra volume should have earned.

Profit and loss analysis in three steps

1. Common size (vertical analysis): each line divided by revenue for the same period.
2. Change (horizontal analysis): each line against last year, and against budget, in dollars and percent.
3. Bridge: last year's operating profit, plus the volume effect, plus a rate effect for each line whose share of revenue moved, equals this year's operating profit.

LY operating profit + Volume effect + Σ Rate effects = TY operating profit

The CFA Institute's reading on financial analysis techniques describes the first two: a vertical common-size income statement "divides each income statement item by revenue", and horizontal analysis compares each item with a base period to show the trend. The bridge turns those two views into one explanation.

This page is the method. For a filled-in statement read line by line, see the profit and loss statement example; for the layout itself, the profit and loss statement template.

The rows you need

Two periods of the P&L at the same level of detail: revenue, cost of goods sold, gross profit, each operating cost line, depreciation and amortization, interest and tax. Public companies follow the captions in the SEC's Regulation S-X, Rule 5-03; a management P&L can be more detailed, but both years must use the same account mapping. If an account moved from G&A to sales and marketing between the years, restate last year first.

Step 1: every line as a percentage of revenue

USD thousands. LY is last year, TY this year.

With revenue in a cell named RevLY, the % of revenue for any line in row 3 is:

=B3/RevLY

and the same with RevTY for this year. Read down the two percentage columns: cost of goods sold took one more point of revenue, sales and marketing half a point more, G&A half a point less. Operating margin fell from 12.0% to 11.0%. The SEC's Beginners' Guide to Financial Statements defines that ratio the same way: income from operations divided by net revenues.

Step 2: what changed year over year

Change is =D3-B3 and change % is =D3/B3-1. A line that grew faster than revenue took a bigger share of it: cost of goods sold (+11.7%) and sales and marketing (+14.6%) did, G&A (+4.5%) did not. Revenue up 10% and net income flat is the headline; the rest of the analysis explains it. Add a budget column beside last year and the same two formulas give the budget variance, covered line by line in variance analysis.

Step 3: the profit bridge

Volume effect = (TY revenue − LY revenue) × LY operating margin

Rate effect per line = −(TY % of revenue − LY % of revenue) × TY revenue

The volume effect is what the extra revenue would have earned at last year's margin. Each rate effect is what a line's change in share of revenue cost or saved on this year's revenue.

Revenue grew 10%, but the gross margin fall absorbed 462 of the 504 the volume should have added. The sales and marketing increase was paid for by the G&A saving. The rise in interest then took the remaining 42, which is why net income did not move. A bridge like this one is the most useful single table in a monthly pack, because every number in it has a cause.

The check

Two identities prove the analysis before anyone reads it:

1. The bridge closes. 5,040 + 504 − 462 − 231 + 231 + 0 = 5,082, the reported operating profit. In ratio terms: LY margin on TY revenue is 12.0% × 46,200 = 5,544, and the rate effects take it down by 1.0 point × 46,200 = 462 to 5,082.
2. The percentages add up. Down to operating profit, the common-size column must close: 100.0 − 64.0 − 12.5 − 9.5 − 3.0 = 11.0%, and 100.0 − 63.0 − 12.0 − 10.0 − 3.0 = 12.0% for last year.

Then tie revenue, operating profit and net income to the trial balance for each year.

Going below the lines

The bridge says gross margin cost 462; it does not say why. Three things move gross margin: price, cost and mix, as set out in gross profit margin. Split revenue and cost of goods sold by product line and by customer, and find out whether the point came from discounts, supplier costs, or more revenue from low-margin lines. Split sales and marketing and G&A by cost center, to see whether the half-point rise is headcount, campaigns or commissions on the extra revenue. Each split must sum back to the line in the P&L.

Where it goes wrong

• Account mapping changed between years. A line moves with no real change; check the chart of accounts before reading any movement.
• Big percentages on small lines. A 50% jump on a $20,000 line is not a finding. Set a threshold in points of revenue as well as in percent.
• One-time items left inside ordinary lines. Restructuring costs or asset-sale gains in either year distort the trend; show them on their own line.
• A 53-week year against a 52-week year. The extra week adds about 1.9% to every line; adjust or compare weekly averages.
• A bridge that does not close. A gap labeled "other" means the analysis is unfinished.

The P&L analysis from your ledger, every month

Covirage maps the ledger once and its tools produce the common-size P&L, the change table and a bridge that must close to reported operating profit; the external AI model drafts the commentary from those figures and never does the arithmetic. See FP&A reporting for the same three steps run on your own ledger export each month. For the revenue bridge in more detail, see price volume mix; for EBITDA against operating profit, EBITDA vs operating income.