Your .mdb files are on borrowed time. Windows 11 defaults to 64-bit Office, which cannot load the Jet 4.0 engine that .mdb depends on. The format has known security vulnerabilities that Microsoft will never patch. And every month you delay, you accumulate more technical debt that makes the eventual conversion harder.
This guide compares every realistic method for converting .mdb to .accdb in 2026 — from free manual approaches to dedicated conversion software. If you want a step-by-step walkthrough instead, see our complete .mdb to .accdb conversion guide. I have tested each option on real-world databases with VBA, linked tables, and ActiveX controls. Here is what actually works.
Three forces are converging to make .mdb files unviable:
The Jet 4.0 database engine is 32-bit only. Windows 11 installs 64-bit Office by default. When users open a .mdb file in 64-bit Access, they get a cryptic error about the database engine not being found. You can force 32-bit Office installation, but that limits other applications and is not a supported long-term configuration. For a full breakdown of this issue, see Access Database Not Working on Windows 11.
The .mdb format stores VBA code in an executable container with no sandboxing, no code signing, and no modern security model. It is a known malware vector. IT security teams are blocking .mdb files at the email gateway and network share level. Even if your file works today, your organization's security policy may block it tomorrow.
Microsoft has not updated Jet 4.0 since 2010. The ACE engine (which powers .accdb) receives regular updates, supports modern data types, and integrates with current Office features. Building on .mdb means building on a dead platform.
| Method | Price | VBA Fixes | Provider Updates | Validation |
|---|---|---|---|---|
| Manual (File > Save As) | Free | No | No | No |
| MS Database Migration Tool | Free | Partial | No | Limited |
| LegacyLeaps | $99-$347 | Yes | Yes | Yes |
| Full Convert (Spectral Core) | $499+ | No | N/A | Partial |
| Bullzip MS Access to MySQL | Free | No | N/A | No |
| Manual Consulting | $10K-$40K | Yes | Yes | Yes |
Cost: Free
Open the .mdb in Access. Click File, Save As, choose .accdb format. Done — if your database is simple.
The problems with this approach are severe for any real-world database:
Use this method only for single-table databases with no code, no forms, and no linked objects. For anything else, you are creating a time bomb.
Cost: Free
Microsoft released a migration assistant that scans databases for compatibility issues. It identifies some problems but does not fix them automatically. It flags deprecated features and generates a report.
Limitations:
Useful as a free diagnostic step, but it is not a converter. It tells you what is broken without fixing it.
Cost: $99 (Standard) / $347 (Pro)
LegacyLeaps is built specifically for the .mdb-to-.accdb use case. It runs locally on your machine — your database never leaves your network. The conversion handles everything the manual method misses:
The free scan shows your database's complexity tier before you pay anything. Standard tier covers databases with tables, queries, and basic forms. Pro tier covers VBA modules, ActiveX controls, linked tables, and Jet SQL rewrites.
The LegacyLeaps scanner identifies every compatibility issue in your database. No payment required. No file upload — it runs locally.
Run the Free ScanCost: $499+ (Pro license)
Full Convert is a database migration tool focused on moving data between different database engines — Access to SQL Server, MySQL to PostgreSQL, Oracle to Access, and so on. It handles schema conversion and data transfer competently.
However, it is the wrong tool for .mdb-to-.accdb conversion:
If you need to move your Access data to SQL Server or PostgreSQL, Full Convert is a solid choice. For .mdb to .accdb specifically, it solves the wrong problem.
Cost: Free
Bullzip exports Access table data to MySQL. That is all it does. It does not produce an .accdb file. It does not preserve forms, reports, queries, or VBA. It is listed here because it appears in search results for "mdb converter" — but it converts to the wrong target format entirely.
If your goal is to keep an Access database running as an Access database, Bullzip is irrelevant.
Cost: $10,000-$40,000 per database application
Hiring a consultant or development firm to manually convert your Access application means paying senior developer rates ($150-$300/hour) for weeks or months of work. This makes sense only for large, complex applications with hundreds of forms and tens of thousands of lines of VBA — the kind of database that is effectively a custom business application.
For most .mdb files — even those with moderate VBA — consulting is dramatically overpriced. A 50-table database with 2,000 lines of VBA does not need a $25,000 engagement. It needs software that handles the mechanical work (PtrSafe, provider updates, control mapping) and a validation pass to confirm the output.
Not all conversion tools are equal. Here is what separates a real converter from a file renamer:
The converter must scan every VBA module, identify 32-bit API declarations, and inject PtrSafe keywords with correct LongPtr type substitutions. Simply copying VBA into the new file without fixing it defeats the purpose of conversion — the code will crash on first run in 64-bit Office.
Every reference to Microsoft.Jet.OLEDB.4.0 must become Microsoft.ACE.OLEDB.12.0. This applies to linked table definitions, ADO connection code in VBA, pass-through queries, and DSN-less connections. Miss one, and users get "unrecognized database format" errors on random operations.
Your Access database contains business data — customer records, financial information, proprietary processes encoded in VBA. A converter that uploads your file to a cloud server introduces unnecessary risk. Look for tools that process everything locally on your machine.
After conversion, you need proof that the output matches the input. A proper converter generates a report comparing table counts, record counts, query definitions, form bindings, and VBA module status between the source .mdb and the output .accdb. Without this, you are trusting blindly.
The process takes under five minutes for most databases:
Start with the free scan to see exactly what is in your database. Then choose your tier — Standard for simple databases, Pro for VBA-heavy applications. 100% money-back guarantee if the output does not preserve your data and code.
View PricingYes. LegacyLeaps converts .mdb to .accdb without requiring Access to be installed. It runs locally on Windows and handles VBA fixes, provider updates, and ActiveX mapping automatically. Most free methods (like File > Save As) do require a licensed copy of Access.
Not automatically. VBA code with 32-bit API declarations (Declare statements without PtrSafe) will break in 64-bit Office. A proper converter adds PtrSafe keywords, updates pointer types to LongPtr, and fixes DAO/ADO references. LegacyLeaps handles all of this. The manual "Save As" method does not touch VBA.
Partially. Windows 11 ships 64-bit Office by default, which cannot use the Jet 4.0 engine. You can force 32-bit Office as a workaround, but this limits other applications and is unsupported long-term. Converting to .accdb is the only forward-compatible path.
The .mdb format uses legacy Jet 4.0 (32-bit only, no modern security). The .accdb format uses the ACE engine — 64-bit compatible, field-level encryption, attachment data types, multi-valued fields, and active support from Microsoft. For a deeper dive into these differences, read MDB vs ACCDB: What Changed.
LegacyLeaps charges $99 (Standard) or $347 (Pro) per database. Manual consulting runs $10,000-$40,000 for complex applications. The free scan identifies your exact tier before you pay anything.
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