What this tool does
This is a free, browser-only API cost calculator for any pay-per-use API billed by request, by 1,000 units, or by GB — payment gateways, SMS/email providers, maps and geocoding, object storage, search, or an internal service you charge back to teams. Unlike a token calculator built only for LLM pricing, you define each plan's free monthly allowance, flat base fee, and up to three graduated rate tiers yourself, so it works for any vendor's real pricing page. Enter your volume once and compare up to four plans side-by-side, see which one wins today, and find the exact point where a cheaper plan takes over as you scale.
How to use it
Set your monthly volume (or let the per-day hint guide you), an expected monthly growth rate, and a projection window. For each plan, enter its name, free units included per month, a flat monthly base fee if any, and up to three tiers: a rate for the first block of paid volume, a rate for the next block, and a rate that applies to everything beyond that. Click Compare costs. You get a stat card and table row per plan showing cost today, cost at the end of the projection window, and total spend over that window, plus the volume at which any two plans swap places in cost, and an inline chart of cost versus volume so you can see the crossover visually.
Example 1 — pay-per-request vs. flat subscription
Plan A — Pay-as-you-go
Free: 0 · Base fee: $0/mo Tier 1: unlimited @ $0.0025 / unit
Plan B — Flat subscription
Free: 0 · Base fee: $199/mo Tier 1: unlimited @ $0 / unit
Output at 60,000 units/month
Plan A: 60,000 × $0.0025 = $150.00/mo Plan B: $199.00/mo (flat) Cheaper today: Plan A, by $49.00/mo Crossover point: 79,600 units/month (0.0025 × 79,600 = $199.00 = Plan B's flat fee)
Example 2 — graduated tiers with a free allowance
Plan — Tiered email-style API
Free: 3,000 units/mo · Base fee: $0/mo Tier 1: up to 50,000 @ $0.00080 / unit Tier 2: up to 100,000 @ $0.00060 / unit Tier 3 (remainder): @ $0.00040 / unit
Output at 120,000 units/month
Billable volume: 120,000 − 3,000 free = 117,000 Tier 1: 50,000 × $0.00080 = $40.00 Tier 2: 50,000 × $0.00060 = $30.00 Tier 3: 17,000 × $0.00040 = $6.80 Total: $0.00 base + $40.00 + $30.00 + $6.80 = $76.80/mo
How graduated tier billing is calculated
Most usage-based APIs bill like income tax brackets, not like a single flat rate applied to your whole volume. The calculator first subtracts your free monthly allowance, then fills each tier in the order you defined it — charging that tier's rate only for the units that fall inside it — before spilling the remainder into the next tier. If your volume exceeds every tier you defined, the last tier's rate is applied to everything beyond it, since real vendor pricing pages always define an open-ended final tier. This produces the same number the vendor's own invoice would show, instead of the common mistake of multiplying total volume by one rate.
How the crossover point is found
For any two plans, monthly cost as a function of volume is piecewise linear and increasing, because each tier adds a straight per-unit charge on top of the previous tier's total. The tool samples both cost curves across a wide volume range, watches for the point where the difference between the two curves changes sign, then linearly interpolates between the two nearest samples to report an accurate crossover volume rather than a rounded guess. If the curves never cross in the scanned range, it reports which plan stays cheaper throughout instead of showing a meaningless number.
FAQ
Is this only for LLM/token pricing like GPT or Claude?
No. For token-based LLM pricing use the dedicated LLM Token Cost Calculator on this site. This tool is for any pay-per-use API billed by request, by 1,000 units, or by GB: payments APIs, SMS/email APIs, maps and geocoding, storage, search, or internal microservices you charge back internally. You define the free tier, base fee, and graduated rate tiers yourself, so it works for any provider's pricing page.
What is graduated (tiered) pricing and how does the calculator apply it?
Graduated pricing charges different rates for different slices of your volume: the first block of usage at one rate, the next block at a lower rate, and so on, the same way income tax brackets work. The calculator subtracts your free allowance first, then fills each tier in order up to its limit before spilling into the next tier, and applies the last tier's rate to any volume beyond the final limit. This matches how most usage-based APIs actually bill, rather than applying one flat rate to your whole volume.
How does the crossover point calculation work?
The tool computes each plan's total monthly cost across a range of volumes from zero up to several times your current volume, then scans for the point where one plan's cost line crosses another's. Because graduated pricing is piecewise linear, the crossing point is found by linear interpolation between the two nearest sample points, giving an accurate volume threshold rather than a rough estimate. If the lines never cross in the scanned range, the tool reports that one plan stays cheaper throughout.
How is the growth projection calculated?
You enter your current monthly volume and an expected month-over-month growth rate. The tool compounds that rate forward for the number of months you choose (volume at month N equals current volume times (1 + growth rate) to the power of N-1), recalculates each plan's tiered cost at every projected month, and sums those monthly costs into a total cost for the whole window. This shows not just what you pay today but which plan wins once you scale past a free tier or into a cheaper bulk tier.
Does this tool send my volume or pricing data anywhere?
No. Every calculation runs in plain JavaScript in your browser tab. There is no server call, no API lookup, and no network request after the page loads, so it keeps working offline and is safe to use with real internal usage numbers or unpublished vendor pricing you were quoted privately.
Can I model a flat monthly subscription against pay-as-you-go pricing?
Yes. Set a plan's base fee to the subscription price and its tier rates to $0 so no per-unit charge applies, and compare it against a second plan with no base fee and a real per-unit rate. The crossover point the tool reports is exactly the volume at which the subscription becomes cheaper than paying per request.