Add Calculated Column to JSON Files Online
Add a new column to JSON files computed from an arithmetic expression over existing columns. No formulas, no code — just point and click.
About this tool
Add a new computed column to a JSON file by combining two existing columns (or a column and a constant) with an arithmetic operator. Multiply a price column by a quantity column, subtract a cost from a revenue, compute a percentage — without opening a spreadsheet or writing code. All calculation runs locally in your browser.
Frequently Asked Questions
What arithmetic operations are supported when adding a column to a JSON file?
Addition (+), subtraction (−), multiplication (×), division (÷), and modulo (%). You can combine two columns, two constants, or one column and one constant.
What happens if I divide by zero when calculating a column in a JSON file?
Division by zero returns NULL rather than throwing an error. The resulting column will have NULL in any row where the divisor is zero or null.
Can I chain multiple calculations in a JSON file?
This tool adds one calculated column at a time. To chain calculations — for example, first compute revenue = price × quantity, then profit = revenue − cost — run the tool twice. Each run adds the new column to the downloaded result.
Is my data private?
Yes — completely. Your file is never uploaded to any server. Everything runs locally in your browser using WebAssembly — processing happens entirely inside your tab. Once you close the tab, nothing is retained.
What is the maximum file size?
The free limit is 50 MB. For larger files, performance depends on your device's available memory — most modern machines handle 500 MB to 1 GB comfortably.
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