Backlog Explained

Backlog measures the dollar value of contracts a company has signed but not yet delivered or recognized as revenue. It's the visibility metric for project-based, long-cycle, and capital equipment businesses because it tells investors how much future revenue is already locked in. A growing backlog signals demand strength; a shrinking backlog often warns of demand softening before reported revenue reflects it.

What it measures

The general definition:

Backlog = Contracted Future Revenue Not Yet Recognized

The specific calculation varies by industry:

• Defense and aerospace: Funded backlog (firm contracts with appropriated funds) plus unfunded backlog (signed contracts pending appropriations).
• Capital equipment: Customer orders not yet shipped.
• Construction and engineering: Contracted project value not yet performed.
• Enterprise software: Sometimes called "remaining performance obligations" (RPO), the contracted future revenue.

If $LMT reports backlog of $160B and annual revenue of $67B, the backlog represents roughly 2.4 years of revenue visibility. The defense industry typically operates with multi-year backlogs because programs span years from contract award to delivery.

The backlog-to-revenue ratio is a useful diagnostic:

Backlog Coverage = Backlog ÷ Annual Revenue

• Below 1x: Limited visibility. Revenue depends on continuous order flow.
• 1-2x: Moderate visibility. Typical for industrials.
• 2-4x: Strong visibility. Common in defense and capital equipment.
• Above 4x: Exceptional visibility. Usually indicates either long program cycles or strong recent order flow.

How to use it in practice

Backlog matters most for businesses with long execution cycles where revenue lags orders by quarters or years. Defense, aerospace, capital equipment, and large-scale construction are the natural habitat.

$LMT and other defense majors operate with backlogs of 2-3x annual revenue, reflecting multi-year program cycles. Strong backlog growth typically precedes revenue growth by 12-24 months, making backlog one of the most useful leading indicators in defense.

$BA's backlog of approximately $530B (across commercial and defense) represents over a decade of revenue at current production rates. The visibility is enormous but execution risk (production delays, quality issues) determines whether backlog converts to revenue on schedule.

$ASML's backlog of approximately €40B reflects the long lead times for advanced lithography systems. Order momentum in this backlog is a critical leading indicator for the entire semiconductor capital equipment cycle.

$CAT and other heavy equipment makers track backlog quarterly because it provides earlier signal on construction and mining capex cycles than reported revenue.

The book-to-bill ratio is the trajectory metric:

Book-to-Bill = New Orders Booked ÷ Revenue Recognized

• Above 1.0: Backlog is growing. Order momentum exceeds delivery rate.
• Equal to 1.0: Backlog is stable.
• Below 1.0: Backlog is shrinking. Revenue will likely decline if trend continues.

Book-to-bill below 1.0 sustained for multiple quarters typically precedes revenue declines for businesses with backlog visibility.

The composition of backlog matters as much as the total:

• Funded vs unfunded backlog: For defense, only funded backlog represents committed revenue. Unfunded backlog requires future congressional appropriations.
• Cancelable vs non-cancelable: Some backlog can be canceled by customers without significant penalty; some is firm.
• Short-term vs long-term backlog: The portion expected to convert to revenue within 12 months is more reliable than longer-dated portions.

Common mistakes

Treating all backlog as equivalent. A defense contractor's funded backlog and a software company's deferred revenue have different reliability profiles. Always check what's actually contracted versus what depends on future events.

Ignoring the conversion timing. A $100B backlog converting over 10 years generates different annual revenue than the same $100B converting over 3 years. Always check expected conversion timing.

Failing to monitor book-to-bill trends. Stable absolute backlog can hide deteriorating order momentum if revenue is growing while orders are slowing.

ACCE perspective

Backlog isn't in our standard scoring system because it applies primarily to defense, aerospace, and capital equipment businesses. For these companies, we track backlog and book-to-bill trends in our financial models as primary leading indicators of forward revenue.

For investors evaluating long-cycle businesses, the combination of strong backlog coverage (2x+ revenue) with book-to-bill above 1.0 is the foundation of forward visibility. Businesses meeting both thresholds typically deliver more predictable revenue trajectories than businesses dependent on continuous order flow.