Spreadsheets to ERP: It's Complexity, Not Size

You have 20 employees and your spreadsheets work fine. Your competitor has 20 employees and their spreadsheets are falling apart. The difference is not the people. It is the complexity of what each business actually does.

Most advice about when to move from spreadsheets to ERP uses headcount as the trigger. “Once you hit 25 people, it’s time.” “At 50, you need a system.” But headcount is a terrible proxy for what actually breaks spreadsheets. A 15-person import company managing three currencies, two warehouses, and customs paperwork across four countries will hit the wall long before a 100-person firm that sells one product domestically.

The trigger is complexity, not size. And if you are measuring the wrong thing, you will switch too late or too early.

What Complexity Looks Like in a Spreadsheet

Complexity is not about having a lot of data. It is about how many things depend on each other.

A simple business can run on spreadsheets indefinitely. Revenue comes from one source, expenses are predictable, and reporting is straightforward. Add any of the following and the cracks start showing:

• Cross-references between files. Your sales tracker feeds into your billing sheet, which feeds into your revenue report. If someone updates one and not the other, you get a number nobody can trace.
• Multi-currency or multi-entity operations. The moment you invoice in two currencies and report in a third, your Excel formulas become a maintenance burden that only one person understands.
• Approval chains that cross departments. Purchasing needs finance sign-off, which needs ops confirmation. In a spreadsheet, this means emails, copies, and manual status tracking.
• Version-dependent decisions. If anyone in the company has ever asked “which version of this file is the right one?”, that is a complexity signal, not a size signal.

A systematic review of spreadsheet research published in Frontiers of Computer Science found that 94% of business spreadsheets contain errors. Error rates are not evenly distributed, though. They concentrate in spreadsheets with the most cross-references and dependencies, which is exactly the kind that complex operations produce.

Is Your Business Complex Enough to Need a System?

Headcount is easy to measure, which is why people default to it. But a better test for when to move from spreadsheets to ERP is counting your dependencies.

Ask yourself:

1. How many handoffs does a single transaction require? If a sale touches three or more people before it becomes revenue in your books, spreadsheets are not tracking that chain. They are hiding it.
2. How many spreadsheets reference each other? If you update one file and need to update two others to keep your numbers consistent, you already have a system. It is just a fragile one.
3. How many people could leave and take critical knowledge with them? Not just the “spreadsheet wizard,” but anyone who knows which file, which tab, and which formula holds the answer to a recurring question.
4. How many workarounds has your team built? Color codes that mean something only three people understand. Manual copy-paste steps between files every Monday morning. A Slack message that says “check with Maria before closing the month.”

If you scored two or more, the problem is not that you need more people. Your operations have outgrown the tool.

Why Size-Based Timing Gets It Wrong

Waiting for a headcount milestone to justify an ERP decision creates two risks.

You switch too late. A Forrester study on spreadsheet risk found that nearly 90% of business spreadsheets contain errors. For companies with complex operations, those errors compound across departments. By the time you hit the “right” headcount, you have already been making decisions on bad data for months.

You switch too early and overbuy. Some businesses see their competitors adopting ERPs and assume they should too. But if your operations are genuinely simple, a full ERP is overkill. We covered this in detail in our post on why growing businesses overbuy software. The real question is never “are we big enough?” It is “are our operations interconnected enough that a spreadsheet can no longer hold them together?”

The companies that time their switch well are the ones who measure complexity, not headcount. That pattern holds across the mid-size businesses we work with, regardless of industry.

Frequently Asked Questions

How do I know when my business has outgrown spreadsheets?

Count your dependencies, not your employees. If a single transaction touches three or more people, if spreadsheets reference each other, and if critical knowledge lives in one person’s head, you have outgrown spreadsheets regardless of your company size.

Is ERP worth it for a small business?

It depends on operational complexity, not size. A 15-person company with multi-currency invoicing, cross-department approvals, and regulatory requirements will see faster ROI from ERP than a 50-person company with a single product and straightforward billing.

What is the true cost of staying on spreadsheets?

Beyond the direct time spent maintaining files, the hidden cost is decision quality. When 94% of business spreadsheets contain errors, every report built on those files carries risk. The cost compounds as operations grow more interconnected.

How Tier2 Keel Fits Complex Operations

Tier2 Keel was built for the kind of complexity described above: businesses where a single transaction crosses departments, currencies, and approval layers. Instead of bolting on modules you do not need, Keel covers the full business lifecycle from leads through invoicing and settlement in one system.

The cross-department handoffs that break spreadsheets become structured workflows. Multi-currency operations that require manual reconciliation are handled natively. And the knowledge that used to live in one person’s head gets captured in the system itself.

See how Keel works or book a walkthrough.

The question was never “are we big enough for software?” It was always “are we too interconnected for spreadsheets?” If you are counting dependencies instead of desks, you will know exactly when it is time.