# API Gateway Request Cost Calculator

> Estimate a monthly API gateway bill from request volume, a free allowance, two per-million price tiers and response data transferred out.

Category: Software, cloud & AI · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/api-gateway-request-cost-calculator

API gateways usually charge a price per million requests, often cheaper above a volume threshold, plus data transfer for responses. Enter your own rates.

Also called: API request pricing calculator.

## Inputs
- Requests per month (unit million; default 500)
- Free requests (unit million; default 1; optional)
- First price tier covers (unit million; default 300; optional)
- Price per million (first tier) (default 3.50)
- Price per million above the first tier (default 2.80; optional)
- Average response size (unit kB; default 2; optional)
- Data transfer price per GB (default 0.09; optional)
- Currency

## Results
- Monthly cost
- Request charges
- Data transferred out
- Data transfer charges
- Effective price per million requests
- Billable requests (million)

## Formula

```
Billable = Requests − Free;  Request cost = min(Billable, Tier) × P1 + max(0, Billable − Tier) × P2;  Transfer GB = Requests × Response kB ÷ 1,000,000
```

Where:
- Requests, Free, Tier: in millions of requests
- P1, P2: price per million requests
- Response kB: average response size in kilobytes (1,000 bytes)

## Worked example
1. Billable: 500 − 1 = 499 million.
2. Requests: 300 × 3.50 + 199 × 2.80 = 1,050 + 557.20 = 1,607.20.
3. Transfer: 500,000,000 × 2,000 bytes = 1,000 GB × 0.09 = 90. Total 1,697.20.

**Result:** At these example rates, 500 million requests with 2 kB responses cost about 1,697 a month.

## What the result means

Compare the effective price per million with alternatives such as a load balancer or a different gateway type; at high volume the per-request charge can exceed the compute behind it.

## Assumptions and limits
- The free allowance is taken from the first tier.
- Every request returns the average response size.
- Caching, WebSocket connection minutes, custom authorisers and the backend’s own costs are not included.

## Questions

### Do request headers count towards data transfer?

Usually yes. If you know the full response size on the wire, use that instead of the body size.

### Why is the effective price lower than the first-tier price?

Requests above the tier are charged at the lower second price, so the average falls as volume rises.

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/api-gateway-request-cost-calculator