CSV vs Parquet: File Size Test With 100,000 Rows

We tested it ourselves: a 100,000-row CSV file and the Parquet file made from it. Here are the real numbers.

How the test was done. We generated an orders file with 100,000 rows and 7 columns: order_id, customer, email, city, amount, order_date and status. As a CSV it is 6.87 MB. We converted it with the Data Utility CSV to Parquet converter in a Node test, using the same conversion code the website uses, and measured the output. We then wrote the same table with the pyarrow library to compare other compression settings.

The results. The CSV is 6.87 MB. Gzip on the CSV gives 1.41 MB. The Parquet file from Data Utility is 1.84 MB, about 73 percent smaller than the CSV. Parquet written by pyarrow with snappy compression is 1.88 MB, with zstd 1.36 MB and with gzip 1.30 MB. The Data Utility conversion of all 100,000 rows took under half a second in the test. Your numbers will differ with other data, but the pattern is typical.

What the numbers mean. Parquet beats a plain CSV by a wide margin, because it stores each column together and compresses repeated values such as city and status very well. A gzipped CSV can be about as small, but you must unpack the whole file before you can read it. Parquet keeps a type for every column and lets tools read only the columns they need, which makes queries much faster. In our file order_id was stored as an integer and amount as a decimal number, so no values were turned into text by mistake.

When to choose Parquet. Use it when a file is large, when you query it with tools such as DuckDB, Spark, BigQuery or pandas, or when you want to keep column types. Keep CSV when a person will open the file in a text editor or a spreadsheet, or when the receiving system only reads CSV. The best choice for sharing with analysts is often both: CSV for a quick look and Parquet for the analysis.

Open the CSV to Parquet converter

Related tool pages

  • JSON, CSV, Parquet and Excel Converter: Convert between JSON, CSV, Parquet and Excel online for free, one file or a whole folder. It runs in your browser, so nothing is uploaded.
  • JSON to CSV Converter: Convert JSON to CSV online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
  • CSV to JSON Converter: Convert CSV to JSON online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
  • JSON to Parquet Converter: Convert JSON to Parquet online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
  • Parquet to CSV Converter: Convert Parquet to CSV online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
  • Parquet to JSON Converter: Convert Parquet to JSON online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.

How to use the CSV to Parquet converter: step by step

  1. Open the CSV to Parquet converter.
  2. Drop in your CSV file.
  3. Convert and compare the size of the downloaded file.
  4. Keep both files if you are not sure which one you need.

When to use the CSV to Parquet converter

  • Decide if converting a big CSV is worth it
  • Estimate the storage saved on a data lake
  • Explain Parquet to a colleague with real numbers
  • Pick a compression setting

Example

Input: id,name,age 1,Ada,36 2,Alan,41

Output: A Parquet file with the same columns (id, name, age) and typed values.

Frequently asked questions

How do I convert CSV to Parquet?

Drop your CSV file (or paste the data), check the options, click Convert and download the Parquet result.

How big can a file be?

It depends on your device. A few hundred MB usually works.

Which conversions does the Format Converter support?

Any direction between JSON, CSV, Parquet and Excel (.xlsx), for one file or a whole folder. Nested JSON is flattened into columns such as address.city. For Excel, the first sheet is read; old .xls files are not supported.

Why did my number or date change after converting?

Types are detected from the values. Turn off "Detect types" to keep everything as text, which also keeps leading zeros in IDs and phone numbers.

Tip: Repeated text values, such as city or status, shrink the most. Columns of unique text, such as emails, shrink less.