How this instrument works
Trailing twelve months (TTM) is the sum of the four most recently reported quarters, not the four quarters ending on a company's official fiscal year-end. An annual figure only updates once a year, at the 10-K. A TTM figure rolls forward every time a new quarter closes: the oldest of the four drops out and the newest reported one takes its place, so the twelve-month window stays current instead of going stale for most of the next year.
The formula is a plain sum rather than an average or a projected estimate because each of the four inputs is a real, already-reported figure — adding them keeps whatever seasonal pattern the underlying business actually has, instead of erasing it the way multiplying one quarter by four would. An equity analyst pricing a stock mid-year against a trailing P/E, a lender checking a covenant written on TTM EBITDA, and a subscription company's finance team reporting revenue between annual filings all reach for the same rolling sum rather than waiting for the next annual report.
A TTM figure is a working estimate, not an audited one. It is built from interim quarterly numbers that are typically unaudited or only lightly reviewed, so a restatement, a reclassification, or a one-off item recognized differently between quarters can leave the rolling total a little off from what eventually shows up in the audited annual filing. It also says nothing on its own about direction — a $435,000 total looks identical whether the business is accelerating into its strongest stretch yet or coasting on one unusually large period that is about to roll off the back of the window.
- Enter the oldest of the four reported quarters into "Quarter 1 (oldest), $".
- Enter the next two quarters, in order, into "Quarter 2, $" and "Quarter 3, $".
- Enter the most recently closed quarter into "Quarter 4 (most recent), $" — the one that just reported.
- Read "Trailing twelve months (TTM) total, $" for the rolling sum as of the end of Quarter 4.
- Next quarter, drop the old Quarter 1 figure, shift each remaining number back one slot, and enter the new quarter to roll the window forward.
Worked example — four quarters summing to $435,000
Take a small software company that has just closed its fourth quarter. Quarter 1 (oldest) came in at $100,000, Quarter 2 at $110,000, Quarter 3 at $105,000, and Quarter 4 (most recent) at $120,000. Add the four together: $100,000 + $110,000 + $105,000 + $120,000 = $435,000, and that sum — not the $120,000 most recent period alone, and not $120,000 multiplied by four — is the company's trailing twelve months total the moment Quarter 4 closes.
Three months later, once a new quarter reports, the window rolls forward: the old Quarter 1 figure of $100,000 drops out, and if the new quarter comes in at $130,000, the updated total becomes $110,000 + $105,000 + $120,000 + $130,000 = $465,000. None of the older three quarters changed — only the window shifted, which is the entire mechanical difference between a rolling total and a fixed annual one.
Questions
How is trailing twelve months different from a fiscal year total?
A fiscal year total is fixed to a company's year-end and only updates once a year, at the annual report. Trailing twelve months sums whichever four quarters were most recently reported, so it moves forward every quarter — the oldest one rolls off and the newest rolls on, keeping the twelve-month window current instead of stale for most of the year.
Why not just multiply the latest quarter by four?
Because that erases seasonality. A retailer's holiday quarter or a software company's renewal-heavy quarter can run far above or below the other three, so quadrupling one period over- or understates the year. Summing four already-reported quarters keeps the seasonal swings intact, which is why it tracks a business more faithfully than a single-quarter guess.
Does a TTM figure match the number on the annual report?
Not always exactly. TTM is built from interim quarterly figures that are typically unaudited or only reviewed, while the annual report is audited. A restatement, a reclassification, or a one-time item booked differently between periods can leave the rolling sum slightly off from the audited annual figure — treat it as a close working estimate, not a substitute for the 10-K.
Who actually uses a trailing twelve months figure?
Equity analysts compute a trailing P/E or an EV/EBITDA multiple to value a stock between annual reports. Lenders write loan covenants against a TTM EBITDA threshold so a borrower's health gets checked every quarter, not once a year. Subscription and seasonal businesses lean on it too, since it folds one unusually strong or weak period into a full year of context.
What's the difference between TTM and a 'run rate'?
A run rate takes one recent period and projects it forward, assuming every future quarter looks like the latest one — a forecast built from a single data point. TTM does the opposite: it adds up four periods that already happened, describing the year just completed rather than predicting the one ahead.
References
- Duke Fuqua — Campbell R. Harvey's Hypertextual Finance Glossary
- U.S. SEC Investor.gov — Financial Terms Glossary
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