API Response Size Calculator
Estimate API response size and the effect of field selection.
About API Response Size Calculator
Returning every field regardless of need is the most common source of oversized API responses. At high request volumes the wasted bandwidth becomes a real cost. Field selection is why GraphQL and sparse fieldset conventions exist, and it typically cuts response size by more than half on wide resources.
Formula
API Response Size
Response = records × fields × bytes per field; waste = unused fields × the same product
- sparse fieldsets
- Allowing clients to request only the fields they need
Worked example
With the default values below, API Response Size Calculator returns Response Size of 65.625. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Records returnedminimum 0
- 100
- Fields per recordminimum 0
- 24
- Fields the client actually usesminimum 0
- 8
- Average bytes per fieldminimum 0 bytes
- 28 bytes
- Monthly requestsminimum 0
- 2,000,000
Results
- Response Size
- 65.625 KB
- Response With Only Used Fields
- 21.875 KB
- Wasted Bytes per Response
- 44,800 bytes
- Monthly Bandwidth Wasted
- 83.447 GB
- Possible Size Reduction
- 66.67%
Step by step
- 1Values used
- 2API Response Size
- 3Response Size= 65.625 KB
- 4Response With Only Used Fields= 21.875 KB
- 5Wasted Bytes per Response= 44,800 bytes
- 6Monthly Bandwidth Wasted= 83.447 GB
- 7Possible Size Reduction= 66.67
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is API Response Size calculated?
Response = records × fields × bytes per field; waste = unused fields × the same product Returning every field regardless of need is the most common source of oversized API responses. At high request volumes the wasted bandwidth becomes a real cost.
Why does API Response Size matter?
Field selection is why GraphQL and sparse fieldset conventions exist, and it typically cuts response size by more than half on wide resources.
What values do I need to enter?
This calculator takes 5 inputs: Records returned, Fields per record, Fields the client actually uses, Average bytes per field, Monthly requests. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.