How to Estimate Your Federal Total Addressable Market as an ISV

Every ISV considering federal market entry hears the same number: $100 billion in annual federal IT spend. The number is real. It is also almost entirely useless for planning purposes.

The $100B is the total IT budget across all federal agencies — hardware, software, professional services, networking, and everything in between. The actual federal spend in your specific product category — cybersecurity SaaS for mid-tier DoD components, say, or cloud data analytics for HHS agencies — might be $800M or it might be $40M. And the agency that accounts for 60% of that spend, the typical deal size, and whether there’s room for a new entrant are facts that will make or break your entry strategy.

This guide walks through the methodology for building a federal TAM estimate that is actually useful — using public data, specific techniques, and the honest limitations of what you can know before you talk to agencies.

Why the standard TAM approach fails for federal

Commercial TAM estimation uses analyst reports, market research, and competitive revenue data. Federal market sizing has public transaction-level data available that commercial markets don’t — but it’s structured differently than what most analysts know how to use.

The mistake most ISVs make: They start with a market research report (IDC, Deltek, Gartner) that says “the federal cybersecurity market is $18B.” They apply their commercial win rate. They project $5M in federal sales by year two. Then they spend 18 months and $500K in BD before they discover that the $18B was dominated by three agencies they can’t access, on vehicles that take 3 years to get on, for projects that require a cleared workforce.

The right approach: Start with FPDS and USASpending.gov transaction data. Understand the actual distribution of spend — by agency, by contract action type, by award size, by set-aside eligibility. Then you know what the real market is for a company with your specific profile.

The data sources you need

USASpending.gov

The primary source for federal contract award data. Every federal contract over $10,000 must be reported here. The database goes back to FY2000 and is updated nightly.

Key features:

Search by NAICS code, Product Service Code (PSC), agency, awardee, and keyword
Filter by fiscal year, award type (new, modification, task order), and dollar range
Download full datasets (CSV) for analysis in Excel or Python
The “Advanced Search” lets you build complex queries; results can be exported

USASpending.gov also has an API (api.usaspending.gov) with no key required — you can pull data programmatically if you want to build repeatable analysis.

FPDS-NG (Federal Procurement Data System)

FPDS is the authoritative source of record for contract data and feeds USASpending.gov. It’s accessible via SAM.gov and has a more technical interface with different filtering options. Some analysts prefer FPDS for its more granular data fields; USASpending.gov is easier to start with.

SAM.gov Entity Search

SAM.gov lets you search registered entities (federal vendors) and see their cage codes, NAICS codes, and certifications. This is useful for understanding your competitive landscape — specifically, which companies in your space have SAM registration and what certifications they hold.

Agency Budget Justifications (Congressional Justifications, or CJs)

Every major agency publishes an annual Congressional Budget Justification — a public document submitted to Congress that details their planned spending by program. DoD CJs are particularly useful because they break spending down by program element. You can find them via each agency’s public website or data.gov. CJs tell you what’s planned before it becomes a contract award.

Step-by-step: sizing your federal TAM

Step 1: Identify your NAICS codes and PSCs

Start with your primary NAICS code and all secondary codes that describe your product. For most software companies:

541511 — Custom Computer Programming Services
541512 — Computer Systems Design Services
541519 — Other Computer Related Services
519290 — Web Search Portals, Libraries, Archives
334614 — Software Reproducing (packaged software, physical)

Product Service Codes (PSCs) are a federal classification system separate from NAICS. Software-relevant PSCs include:

7030 — ADP Software
7010 — ADPE Including Firmware
D3xx — IT and Telecom (varies)

Search USASpending.gov by NAICS code first; refine with PSC to narrow to software-specific spend.

Step 2: Pull total category spend by NAICS code

In USASpending.gov:

Go to Advanced Search → Award Type → Contracts
Filter: NAICS Code → [your codes]
Time range: FY2021–FY2025 (5-year view)
Leave other filters open to see total market

Record: total obligated amount, total number of transactions, number of unique awardees.

This gives you the total addressable federal spend in your category over 5 years. Divide by 5 for an annual average; look at the year-over-year trend.

Step 3: Break down by agency

In the same search, filter by “Awarding Agency” and run the top 10 agencies by spend. For most software categories, you’ll find that 3–5 agencies account for 60–75% of total spend.

For each of your top 5 agencies:

What is their annual spend in your category?
Is it growing or declining over the 5-year period?
What percentage is DoD vs. civilian?

This agency concentration analysis is what turns a headline TAM into an actionable targeting list.

Step 4: Analyze award size distribution

Filter your search results by award dollar amount. Look at the distribution:

How many awards were under $150K (micro-purchase or simplified acquisition threshold)?
How many were $150K–$2M?
How many were over $10M?
What is the median award size?

This tells you what the actual buying unit is. If 80% of contracts in your category are over $10M, you’re looking at a market dominated by large primes with extensive past performance — your entry strategy requires teaming, not a direct prime contract. If 60% of awards are under $500K, there’s a robust market for direct contracting without a large team.

Step 5: Map the competitive landscape from FPDS data

Search USASpending.gov by NAICS code and filter for the top 25 awardees by total obligated amount. For each major awardee:

What is their total annual federal revenue in this category?
Do they hold any certifications (8(a), HUBZone, SDVOSB)?
What vehicles do they use?

You’ll see a mix of large primes (Leidos, SAIC, Booz Allen Hamilton), mid-tier specialists, and small businesses. The large primes dominate by dollar volume but lose to specialists on small task orders and set-asides.

Look specifically at award trends: are new entrants winning contracts, or is spend concentrated with the same 5–10 companies year after year? A concentrated, static competitive set is a signal that market entry requires teaming — not direct competition.

Step 6: Calculate your serviceable obtainable market (SOM)

TAM is what exists. SOM is what you can realistically win in 3–5 years. Apply realistic filters:

Filter 1: Accessible agencies Remove agencies where you have no relationships and no realistic path to develop them in 3 years. If your top agency is NSA and you have no cleared personnel, remove it.

Filter 2: Accessible vehicles Remove awards made on vehicles you don’t have and can’t reasonably get on in 3 years. If 70% of awards in your category are on SEWP V and you’re not a SEWP prime, remove that 70% or replace it with the subcontracting share.

Filter 3: Set-aside eligibility If you’re eligible for small business set-asides (SBSA), apply the set-aside percentage to focus on competitions where you’re not facing large primes directly. If you’re not small business eligible, remove set-aside competitions from your SOM.

Filter 4: Deal size fit Remove awards where the typical deal size is below your minimum economical engagement ($500K? $1M?) and above what you can manage without substantially more headcount.

After applying these filters, your remaining number is your realistic SOM — the market that’s actually accessible to a company with your specific profile, certifications, and resources.

Reading the numbers: common patterns

Pattern 1: Category too large, concentrated at top

If your TAM is $5B+ and the top 3 primes control 70%+ of spend, the effective market for a new entrant is the subcontracting opportunity and the small business set-aside slice. Reframe your entry as a subcontracting play, not a prime competition.

Example: Large-scale DoD IT services (NAICS 541512) is dominated by Leidos, Booz Allen, SAIC. A new SaaS company entering this category should identify specific DoD programs where their technology differentiates — not try to compete on prime contract bids with the incumbents.

Pattern 2: Category small but growing

A $200M category growing at 30% annually is often better than a $2B category growing at 3%. Growth signals unmet demand and new budget allocation, which means new entrants have a better shot — incumbents don’t have 20-year relationships with budgets that didn’t exist 3 years ago.

Example: Federal AI/ML spend (NAICS 541519 + PSC 7030) has grown significantly since FY2020. Companies like Anduril Industries and Palantir built significant government revenue by entering a growing market early.

Pattern 3: Agency-specific niche

Your TAM might be $100M total but 65% concentrated at one agency. If that agency has a champion for your technology and you can develop that relationship, the concentrated nature works in your favor — you don’t need to spread across 50 agencies, you need to win 1 agency deeply and use it as a reference site.

Using GovExpress for TAM research

The methodology above works but is manual — it takes 40–80 hours to do rigorously, and keeping it updated requires repeating the analysis when you’re evaluating new agency targets or NAICS codes.

GovExpress automates this process: our platform queries USASpending.gov, FPDS, and SAM.gov in real-time to produce your Federal TAM analysis as part of the Federal Readiness Report. The output includes:

Your total federal spend by NAICS code, with 5-year trend
Agency concentration analysis — which agencies account for what share
Award size distribution for your category
Top awardees with their contract vehicles and certifications

Score your company and get your federal TAM →

What TAM sizing cannot tell you

TAM analysis tells you what has been purchased. It doesn’t tell you:

What agencies plan to buy next year (check agency CJs and forecast portals for that)
Whether your specific product will win against incumbents (requires BD conversations)
Which contracting officers are actually buying new technology vs. renewing legacy contracts

The best TAM analysis narrows your targeting. The actual market entry still requires relationships — TAM data tells you which relationships to prioritize.