API cost calculator and plan comparison

Name: API cost calculator
Author: Richard Injante

Monthly and annual spend on an API with a fixed fee and volume pricing, to compare up to three plans and see when each one pays off.

Content reviewed by Richard Injante Published by SolucionesAhora.com Updated on 2026-10-08 How we verify

Calculator inputs

Enter your figures, or press “See example” to watch it work.
If your case is unusual, open “Advanced options”.
Read the result and, below it, what it means and how it was worked out.

Requests per month

How many API calls you make (or will make) per month.

Expected monthly volume

Plan 1: price per 1,000 requests over the allowance

What the plan charges for every thousand requests above those included.

On requests not included

Plan 1: included requests (optional)

The requests already covered by the plan’s fixed fee.

Inside the fixed fee

Plan 1: fixed monthly fee (optional)

What you pay even if you do not use the API

Advanced options

Monthly volume growth (optional) %

If usage grows every month, enter the percentage: the annual cost is worked out with volume rising month by month for 12 months (negative if it falls).

To estimate the year

Plan 2: fixed monthly fee (optional)

Optional. Fill in the plan’s three figures to compare it with the first.

Plan 2: included requests (optional)

Plan 2: price per 1,000 over the allowance (optional)

Plan 3: fixed monthly fee (optional)

Optional. Fill in the plan’s three figures to compare it with the first.

Plan 3: included requests (optional)

Plan 3: price per 1,000 over the allowance (optional)

See the result

Results

Plan 1: monthly cost100

Plan 1: annual cost1,200

Plan 1: variable portion100

Plan 1: real cost per request0.000400

Plan comparison
Plan	Fixed fee	Included	Price per 1,000	Cost per month	Cost per year	Per request
Plan 1	0	0	0.4	100	1,200	0.0004

Monthly cost by volume
Requests per month	Plan 1
0	0
50,000	20
100,000	40
150,000	60
200,000	80
250,000	100
300,000	120
350,000	140
400,000	160
450,000	180
500,000	200

See the working step by step

Plan 1: 100 a month

Free, no sign-up! What if you could do this without a calculator? A five-minute game with challenges, lives and points. It clicks even when you cannot be bothered.

In short

What it calculates: Monthly and annual spend on an API with a fixed fee and volume pricing, to compare up to three plans and see when each one pays off.
Formula used: Billable = max(0, requests − included)
Example: Example 1. A single plan.

API cost calculator

Almost every API mixes a fixed fee, an included allowance of requests and a per-thousand price for anything beyond it. That combination makes the real cost per request very different from the headline price, and makes the cheapest plan depend on your volume: at low use the plan with no fee wins; at high use, the one with more included requests.

Enter your volume and the plan’s figures; to compare, add two more plans. You get the monthly and annual cost (with growth, if any), the cheapest plan, how much you save and from what volume it pays to switch. Everything runs in your browser.

How it works

For each plan, included requests are subtracted, the excess is billed at the per-thousand price and the fixed fee is added. Real cost per request spreads the whole bill over every call.

The annual cost adds up twelve months; if usage grows, each month multiplies volume by (1 + growth). The break-even volume between two plans is where they cost the same: below it one is better, above it the other.

Formula

Billable = max(0, requests − included)
Monthly cost = fixed fee + billable ÷ 1,000 × price
Annual cost = sum over 12 months, with volume × (1 + growth)^month
Break-even between two plans: the volume where cost₁ = cost₂ (solved piece by piece)

Worked example

Example 1. A single plan.
250,000 requests a month, 50,000 included, 0.40 per thousand and a fee of 29: variable portion 80, monthly cost 109, annual 1,308 and 0.000436 per request.

Example 2. Three plans.
Plan 1: no fee or allowance, 0.50 per thousand. Plan 2: fee 49, 100,000 included, 0.30 per thousand. Plan 3: fee 199, 1,000,000 included, 0.10 per thousand. At 250,000 requests a month they cost 125, 94 and 199: plan 2 wins, saving 372 a year. Plan 1 is better below 98,000 requests; plan 3, above 600,000.

Example 3. With growth.
The same three plans with 5% monthly growth: plan 2 is still the cheapest (1,421.78 a year) and the saving against plan 1 rises from 372 to 567.86.

Example 4. Heavy volume.
At 3,000,000 requests a month, plan 3 costs 399 a month against 919 for plan 2 and 1,500 for plan 1.

Explanation

How an API is billed by volume

Most combine three elements: a fixed monthly fee, a number of included requests and a price per thousand additional requests. The total cost is the fee plus the excess at its price, and the real cost per request is that total divided by the calls.

Choosing between plans

A plan with a high fee usually includes more requests and charges less for the excess: it pays off at high volume. One with no or a low fee comes out better if you use little. The break-even volume is where they cost the same; look at it against your growth forecast, not just today’s use.

Volume growth

If your usage grows every month, today’s cheapest plan may stop being the cheapest within a few months. Enter your expected growth and compare the cost over 12 months, not just the first.

Common mistakes

Comparing only the fixed fee or only the per-thousand price.
Forgetting that included requests do not roll over from one month to the next (in most plans).
Choosing on today’s use with no growth forecast.
Leaving out separate costs (rate limits, support, taxes).
Switching plans because of a one-off spike in volume.

Limits of this calculator

It models “fee + included + overage price” plans; it does not cover stepped-tier pricing or annual-commitment discounts.
It compares up to three plans.
It does not include taxes, rate limits or support costs.
It assumes volume is the same every day within a month.

Notice

This is an estimate. Check rates and terms on the provider’s official page before you sign up.

Frequently asked questions

Why does cost per request fall as volume grows?

Because the fixed fee spreads across more calls. At low volumes that fee dominates the total.

Is a higher plan worth it?

Compare it here: add the next plan as plan 2. If the monthly cost at your volume (and its growth) is lower, switching pays; if not, it does not.

What is the break-even volume?

The number of requests a month at which two plans cost the same. Below it one is better, above it the other.

How do I work out growth?

Compare the volume of a few months ago with the current one and take the average monthly percentage. If unsure, calculate with 0 and with a cautious value and look at the difference.

Do included requests roll over?

In most plans, no: whatever you do not use in a month is lost. Read your provider’s terms.

Does it work for AI APIs priced per token?

No: for that, use the token cost calculator, which bills by input and output tokens.

What about taxes?

They are not included. Add VAT or whatever taxes apply in your case.

Is my data sent to a server?

No. The calculation runs in your browser.

Sources and references

The formula behind this calculator is not ours. These are the sources it comes from, in APA 7 format, in case you want to go to the original or cite them in your own work.

Grubb, M. D. (2009). Selling to overconfident consumers. American Economic Review, 99(5), 1770–1807. https://doi.org/10.1257/aer.99.5.1770 https://doi.org/10.1257/aer.99.5.1770 Analyses three-part tariffs (fixed fee, included allowance and overage price): hence the real cost per unit depends on volume.

Need to calculate something else?

These tools are often used alongside this calculator.