Spoke · Spreadsheet template · 6 min read

TAM/SAM/SOM template — free Sheets/Excel

Copy this structure into Google Sheets or Excel. Two parallel sections (top-down + bottom-up), formulas, source citations enforced, sanity-check rules.

Block 1: Top-down sizing

Start with industry report. Narrow to your segment. Apply realistic share. The structure forces source citations — every number traces to a published source.

# TOP-DOWN TAM/SAM/SOM A: Layer B: Value C: Formula D: Source TAM (industry) $80B [B2 from source] Gartner CRM 2024 p.42 TAM (your segment) $12B =B2 * 0.15 Same report, "SMB" segment 15% SAM (geo + lang) $4.2B =B3 * 0.35 35% = US + EU English-speaking SAM (channel) $2.5B =B4 * 0.60 60% reachable via SEO + paid (your model) SOM (3-5 yr) $25M =B5 * 0.01 1% capture (anchor: comparable startup at year 5) SOM customers 2,083 =B6 / D7 Avg ACV / customer = $12K ACV $12,000 [your pricing] Pricing model

Block 2: Bottom-up sizing

Start with population, narrow by ICP fit, reachable, capturable. Multiply by ARPU. This grounds your numbers in your actual funnel — top-down validates them.

# BOTTOM-UP TAM/SAM/SOM A: Layer B: Value C: Formula D: Source Population 33,000,000 [count] US Census SMB 2024 ICP fit % 8% [your ICP definition] Service-based SMB filter TAM count 2,640,000 =B2 * (B3/100) TAM $ $3,168,000,000 =B4 * D8 × ARPU $1.2K SAM reachable % 35% [your channel model] Paid + SEO realistic reach SAM count 924,000 =B4 * (B6/100) SAM $ $1,108,800,000 =B7 * D8 SOM capture % 1% [5-year realistic] Anchor: comparable startup SOM count 9,240 =B7 * (B9/100) SOM $ $11,088,000 =B10 * D8 ARPU $1,200 [your pricing] $99/mo SMB SaaS standard

Block 3: Sanity check

Compare top-down and bottom-up. If they\'re within 3x, you\'re probably honest. If they diverge more, find the broken assumption.

# SANITY CHECKS Check Top-down Bottom-up Ratio Pass? TAM $12B $3.2B 3.75x ⚠ widen SAM $2.5B $1.1B 2.27x ✓ pass SOM $25M $11M 2.27x ✓ pass # IF RATIO > 5x: - Top-down likely inflated (segment definition too broad?) - Bottom-up likely underestimated (missed expansion revenue?) - Investigate before sharing with investors

Block 4: Sources log

Every number above must reference a row here. Investors WILL check.

# SOURCES ID Type Citation URL S1 Industry Gartner CRM Market Report 2024, p. 42 [link] S2 Government US Census Bureau, SMB stats 2024 [link] S3 Comparable [Competitor X] capture year 5: $50M [Crunchbase URL] S4 Primary Customer interviews, n=22, March 2026 [internal doc] S5 Internal Pricing model v1, finance team [internal doc]

Skip the spreadsheet for first-pass

The template is for serious decks. For first-pass sanity checks, use our free interactive calculator — same math, no spreadsheet setup.

Open the calculator →Get cited TAM/SAM/SOM

Frequently asked questions

Can I use this template in Google Sheets?+

Yes. The formulas below work identically in Google Sheets and Excel — they're standard SUM/PRODUCT/IF functions. Copy the structure into a new Sheet, then replace placeholders with your numbers.

What's the most important part of the template?+

The Sources column. Every number must trace to a citation — industry report (Statista, IBISWorld), government data (Census, BLS), or your own primary research. Investors check sources. The template enforces citation by making it a required column.

Should I include both top-down and bottom-up?+

Yes. Building both is the only way to sanity-check your assumptions. If they disagree by more than 5x, one method has a hidden assumption that's wrong. The template has parallel sections for both — fill them out, compare, and the gap tells you what to investigate.