Convert Excel to DuckDB
Upload a .xlsx or .xls file and get back a DuckDB file. Types are preserved rather than flattened to text. Free, no registration, up to 10MB.
Click to upload or drag and drop
CSV, Excel, SQLite, SQL, DBF (max 10 MB)
How your data is typed in DuckDB
Generated from the converter's own DuckDB type mapping — this is what it actually emits, not an example.
| Your data | DuckDB type |
|---|---|
| Whole number | BIGINT |
| Decimal (money) | DECIMAL(10,2) |
| Floating point | DOUBLE |
| True / false | BOOLEAN |
| Date | DATE |
| Date and time | TIMESTAMP |
| Short text | VARCHAR |
| Long text | VARCHAR |
| Binary data | BLOB |
Working from an Excel file
"Excel" covers two entirely different file formats, and which one you have decides how much type information survives the conversion. It is worth checking what your workbook was actually saved as before you upload it.
- →Only .xls and .xlsx are recognised. A macro-enabled .xlsm, or a workbook saved as OpenDocument .ods, is refused before anything is read - save a copy as .xlsx first.
- →The two extensions take different code paths inside the reader: .xlsx through openpyxl, .xls through pandas and xlrd, and they do not recover the same amount of information from the file.
- →Sheet names become table names with every character outside letters, digits and underscores replaced one for one, so "Q1 Sales (2024)" arrives as Q1_Sales__2024: the space and the opening bracket each leave an underscore behind, and the trailing one is trimmed.
Decimals and text in the .duckdb file
DuckDB takes the source's declared types more nearly unchanged than any other target here, which makes the two places where it cannot the things worth reading: the width of a decimal, and the length of a string.
- →DECIMAL tops out at 38 digits, so a wider source column is clamped rather than refused: an Oracle NUMBER(50,10) is created here as DECIMAL(38,10), and the scale is never allowed to grow past the precision holding it.
- →A decimal that declared no scale gets six places for its fraction rather than none, inside that same rule: a source precision of 10 becomes DECIMAL(10,6), one of 5 becomes DECIMAL(5,5), and one that declared no precision either becomes DECIMAL(18,6).
- →Strings become VARCHAR with no length attached to them. DuckDB's VARCHAR is unbounded, so no column has to be sized in advance and no row can be turned away for being longer than the column it goes in.
Reading Excel
- →Numbers, dates and booleans are read as Excel stored them, never converted to text and re-parsed.
- →Cell number formats are read out of .xlsx workbooks, so a column formatted as currency becomes a fixed-point decimal rather than a floating-point number — which is how money avoids acquiring a rounding tail. Legacy .xls is the exception: the xlrd path exposes no formats, so its currency columns come across as ordinary numbers.
- →A column formatted as a date becomes a date, not a timestamp at midnight; one formatted with a time keeps its time.
- →One sheet becomes one table. Empty sheets are skipped, and sheet names are sanitised for the target.
Writing DuckDB
- →A real .duckdb file, not a script — open it straight away with the DuckDB CLI.
- →DuckDB has genuine DECIMAL and BOOLEAN types, so nothing is flattened on the way in.
What you get
A ZIP containing database.duckdb. If anything about your data needed a judgement call, a _warnings.txt explains it.
Questions
- Is converting Excel to DuckDB free?
- Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.
- Will my Excel data keep its types in DuckDB?
- Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real DuckDB types rather than everything becoming text. The mapping table above shows exactly what you get.
- Do you store my file?
- No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.