JSON Size Calculator

Estimate JSON Size

Estimate the size of a JSON object based on fields and values

Number of String Fields

Avg String Value Length (chars)

Number of Number Fields

Number of Boolean Fields

Avg Key Name Length (chars)

Array Items (objects with above schema)

API Response Size

Estimate total API response size for a given number of records

Avg Record Size (bytes)

Number of Records

Response Overhead (bytes)

Formula

Size = Sum(keyLength + overhead + valueSize) per field | Gzip ~= Raw * 0.3

Frequently Asked Questions

Why does JSON size matter?

JSON size affects API response times, bandwidth costs, and client-side parsing performance. Large payloads slow mobile apps, increase data transfer costs, and can exceed API gateway limits (e.g., AWS API Gateway has a 10 MB limit).

How much does gzip reduce JSON size?

Gzip typically compresses JSON to 20-40% of its original size because JSON has lots of repetitive structure (keys, braces, quotes). Highly repetitive data can compress to as little as 10% of original size.

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