Market Sizing: What Experts Can Tell You That Reports Can't

The global quantum computing market size in 2025 was valued at US$1.44 billion by one market research company. That same year, another research company provided a different estimated value for the same market - US$3.52 billion.

The huge difference - a factor of 2.4 - apparently points to an error by one of the two companies.

However, neither Precedence Research nor Markets and Markets, the firms behind the estimations, is wrong. The most likely explanation is that each takes into account its own parameters while analyzing a market.

So where do the numbers on market sizing actually come from?

Let’s start from the beginning and analyze where research companies and experts can be more efficient in estimating market sizes.

What Is Market Sizing?

Market sizing is the process in which one attempts to understand just how big a certain market is (in terms of financial value, usually in US$).

It’s possible you may have heard about the two primary methods of calculating market sizing: top-down and bottom-up analysis. These are the main two approaches, but there are certain details that you may have skipped.

Case study

Throughout the article, we will use the following case study to showcase in practice the stages and processes applied in the market-size estimation process.

Say you want to sell 3D-printed biodegradable plastic pet figurines in the United States. For this, you need to define the market:

• Who is the user? Pet owners (primarily dogs and cats) who want a small 3D figure of their pet.
• Who is the buyer? The same pet owners, or gift-givers (family/friends buying for pet owners).
• What is the scope? In the United States only, clients are interested in collectibles or personalized gifts. Focus on custom/3D-printed versions made from biodegradable plastic (not mass-produced resin, porcelain, or traditional action figures).

Bottom-Up vs Top-Down Market Sizing

If you research market sizing, you will definitely come across bottom-up and top-down market sizing methodologies. Read on to learn what each of these means.

Bottom-up market sizing implies that you start with analyzing the simplest aspects (number of customers, number of units, average price) and build up those elements from the bottom to create an overview of the market size.

Formula: (number of units) × (average price) = Market Size

• No. of Units: There are ~95 million U.S. pet-owning households. You assume just 0.4% of these households buy a custom pet figurine in a given year. This gives you 95 million × 0.4% = 380,000 units annually.
• Average Price: Mid-range custom 3D-printed pet figurines currently sell for $40-$90 online, so you use a realistic average of $55.

Bottom-up estimate: 380,000 units × $55 = $20.9 million annually.

The weak point:

Figurines from competitors may be sold with discounts, so if you take into account just the sticker price, without examining what buyers actually pay, you'll overestimate the market.

On the opposite, top-down market sizing means that you begin from a large anchor (like population or GDP) and then narrow down using filters.

Google is your ally for top-down market sizing. Through secondary research, you may discover that an analyst has already published a market size estimate for your market or a very comparable one.

Suggested reading: Primary Research vs. Secondary Research: Which One Does Your Organization Actually Need?

Case study

The global figurine and collectibles market, according to 2025-2026 estimates from multiple analyst reports is ≈$10-12 billion.

North America share is ≈30-35% (around $3.5 billion).

The U.S. share of North America is ≈85-90% (around $3.0-3.2 billion for the broader U.S. figurine market).

The pet/animal segment, together with the custom/personalized segment, is a small slice, around 8-10% of the U.S. figurine market (more popular are licensed action figures, anime, fantasy, etc.). You’re now down to ≈$250-300 million.

You further filter to 3D-printed/biodegradable/sustainable materials and get to 8-10% of the pet/custom segment (which is around $22-28 million).

Top-down estimate: ≈ $25 million annually.

Now you get the idea: you just continue the process with more rigorous assumptions until you get to a place where you're comfortable with (in terms of refining your potential).

The weak point: You inherit someone else's definition of the market (in the intro we mention two different research firms with two different numbers about the quantum computing market), including every error baked into it.

Which Approach is Worth Using?

A short answer is: Two are better than one, so run both.

Experts advise using both market-size approaches to evaluate your market. You should consider determining the market size using each method individually and then calculate the average based on two estimates.

TAM, SAM, and SOM

TAM, SAM, and SOM are the three types of market sizing that can assist you in getting a better understanding of the true size of your business potential.

The table below breaks down each of the three:

The framework itself is universal, but the only thing that is not universal is the numbers you include in this framework.

Let’s go back to our case study market example:

Suggested reading: When and Why Should Startups Work With Expert Networks?

What Industry Experts Can Tell You that Reports Can't

One of the useful things you can do to solve the gap between top-down and bottom-up market-sizing estimates (apart from re-checking your figures and calculations) is to get in touch with people who work inside the market.

This is because people with deep, niche knowledge in the field surface the real boundaries, volumes, pricing, and leakage that desk research can’t see.

So, here are a few examples of how experts can really help you learn more about the market you’re in:

1. Realized pricing, not list pricing

If you talk to a former sales director, there’s a high chance you’ll obtain knowledge about the average discount off list in a competitive deal, which you won’t find in a report. Remember, if realized pricing runs 30% below list price (and your bottom-up model is built on list price), you've overstated the market by 43%.

2. Where the category boundary actually sits

Experts who work directly with customers can tell you which alternative products customers actually switch to and which alternatives they do not consider at all.

3. Demand that is difficult to access

A large potential market does not mean customers can buy immediately. Long procurement cycles, certifications, existing contracts, and regulatory approvals can prevent companies from entering the market for years. Industry experts can help explain how long these barriers typically last.

4. What has changed recently

Market reports can become outdated since most of the time you need months to carry out research and publish it, and a report that is not up-to-date may no longer reflect current reality. Thus, industry experts who work in the market today can provide a more recent view of what is actually happening.

Suggested reading: How Expert Networks Help Leaders to Identify What They Don't Know They Don't Know

It’s important to understand that who is winning in a market can change a lot over ten years, and a company that once was the leading player can lose share to newer competitors. And probably the only way to see it is to talk to people who watched it happen - experts who can provide information that not one available report can.

Example: Three Expert Calls and Their Impact on an Estimate

This is an illustrative example based on typical due diligence work, not a real client.

Before:

A bottom-up model estimated a regional industrial components market at $840 million. It assumed companies charged list prices and factories worked at 90%+ production capacity.

The three calls:

The company’s team had a call with a former sales leader at one of the top-firms in the market, a distributor handling about 20% of regional sales, and a procurement manager at a mid-sized buyer.

What the firm learned:

From the calls, the firm learned that the actual prices were typically 22-28% below list price and that factories were operating at around 65% capacity because demand slowed down.

After:

The estimate fell to $520-590 million. The team used the lower end for its conservative go/no-go decision and kept the higher estimate as an upside scenario.

Remember that a few well-chosen expert calls can uncover assumptions that public data cannot and can turn a single market estimate into a more realistic range.

How to Use Expert Calls in Market Sizing Research

With the help of expert calls, you gain real-world insights that are more accurate than the data in reports available online. These calls can help improve the information you already gained from the two methods of market sizing.

How many calls?

It all depends on the project. For instance, one well-defined segment might require 5 to 10 calls, while if you need to cover several segments or regions, you might need more than 10 calls. The idea here is to spot patterns while learning from independent sources.

Who should you talk to?

Use different perspectives:

• Former industry operators can provide insights on prices and market dynamics.
• Distributors can share information on what actually sells.
• Buyers can tell you what firms buy and why.

Suggested reading: Effective Communication Strategies to Maximize Value from Expert Calls

What if experts disagree?

Disagreements can show that experts might be looking at different segments, regions, or parts of the supply chain, and it’s important that you find the reason behind different insights.

One important compliance rule: Keep expert calls focused on the overall market. Never ask for or use material non-public information about a specific company.

How to Validate a Market Size Estimate

By now, you should have three estimates: top-down, bottom-up, and expert-informed, and your goal is to see whether they point to a similar range.

Use public data, your company’s own data, and expert input together.

Give a range rather than a single number. For instance, instead of saying “$2.5 billion in 2030,” use the range “$2 - $2.8 billion, depending mainly on pricing assumptions,” which is more realistic. Always identify the assumption that has the biggest impact on your estimate.

Keep a simple record of your market sizing process: list each input, its source, and how confident you are in it. Thus, you’ll be able to explain how you got your estimates.

The 20% triangulation rule

Since bottom-up and top-down methods have their own direction of error, you need to triangulate, which basically means running the two methods and the data collected from experts, forcing them to agree.

The bottom-up and top-down need to land within ~20% of each other, but if they differ by 2x or more, revisit your assumptions.

There’s no single authoritative standard that publishes exact universal thresholds, because acceptable divergence depends on many variables, like market maturity or data quality.

Can AI do Your Market Sizing?

Reaching out to a chatbot asking about market sizing is a reasonable instinct, and yet, the honest answer is that AI cannot do your market sizing.

You can use LLMs for structuring certain problems, like asking to carry out a segmentation or sanity-checking your arithmetic.

Chatbots cannot provide data they were not trained on. For example, they can't tell you what discount closed a deal last quarter, because that number was never published anywhere the model could have trained on.

It's crucial that you verify your numbers against a source you can actually name, which might be an expert call or might just as easily be internal transaction data, a regulatory filing, or a direct customer conversation.

Frequently Asked Questions (FAQ)

How do you calculate market size?

Use both bottom-up and top-down, then reconcile them.

• Bottom-up: Number of potential buyers (or units) x average price x purchase frequency.
• Top-down: Start with a published market total and filter by segment, geography, and use case.

Ideally, you should run both methods and treat any serious gap between your figures as information about where your assumptions are weakest (do not noise to average away).

How accurate does market sizing need to be?

Accuracy isn't really the goal. Your goal is obtaining a documented, defensible range, a clear number with its assumptions and sources attached - these are more useful than a single precise-looking figure nobody can trace back to anything.

How do you decide between top-down and bottom-up market sizing?

Consider using both where you can. Top-down is faster when good published data exists for your category, while bottom-up tends to be more reliable when you have strong insight into buyer behavior/unit economics, or when the published totals are broad, or when you're estimating the wrong thing.

Getting to a Number You Can Defend

Every team looking forward to sizing a market can get access to the same published reports.

What can differentiate different teams working on the same question is the step they take after obtaining the insights - did they stop there, or did they go and find someone who could provide them with information unavailable in those reports?

Reports obtained from research companies can tell you how a market looked in the past, but experts who are working (or previously operated within that market) can provide info on what is happening now, like actual prices or how customers use a product.

This is where ENC can help. Our platform connects research teams with experts across industries via 22 expert networks. You gain access to experts in under 48 hours. There are no subscriptions or prepayments.

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