Why this calculator only needs two numbers
Most cost calculators for API vendors are more complicated than the underlying pricing model deserves — dropdown menus for a "tier," a slider for "complexity," a note that says "actual cost may vary." FlowParse's API pricing needs none of that, because there is nothing to select: every page, of every document type, on every plan, bills at the same flat €0.035. Two inputs — how many documents, and how many pages each one averages — are genuinely sufficient to compute an exact figure, not an estimate with a wide error bar.
How the calculation works
monthlyPages = documentsPerMonth × averagePagesPerDocument
monthlyCostEur = monthlyPages × 0.035That's the complete formula — the same one used internally by the calculator above, reading the rate constant directly from the same code path the API itself bills against, so the number can't drift out of sync with real billing.
What this calculator doesn't estimate
Doesn't include a free-plan allowance offset
It shows the raw flat-rate cost for the volume entered — a free plan's monthly allowance would reduce a small-volume bill slightly, not modeled here for a directly comparable figure.
Doesn't add a planning buffer
It's a baseline calculation from exact inputs, not a forecast with margin for estimation error — see the budgeting guide for how to size a buffer on top of this number.
Doesn't model an in-house alternative's cost
This tool is FlowParse's own cost only — a build-vs-buy comparison including infrastructure and reviewer-hours lives in the use-case page linked below.
Getting good inputs for your own numbers
"Documents per month" is usually the easier number — pulled from existing product usage data, a current manual process's volume, or a growth projection. "Average pages per document" is worth getting from a real sample rather than a guess: pull twenty or thirty representative documents and average their actual page counts, since this figure moves the result linearly and is easy to get meaningfully wrong from intuition alone.
| Document type | Typical average pages (starting reference) |
|---|---|
| Invoice | 1–3 |
| Receipt | 1 |
| Bank statement | 2–6 |
| Financial report | 5–30+ |
| Brokerage statement | 3–10 |
Reading the result for three common scenarios
A solo developer testing an idea might enter 50 documents a month at 2 pages each — 100 pages, €3.50 a month, comfortably inside a free plan's allowance. A small SaaS product processing customer invoices might enter 5,000 documents at 2.5 pages — 12,500 pages, €437.50 a month, a real but modest line item. A high-volume fintech might enter 2,000,000 documents at 3 pages — 6,000,000 pages, €210,000 a month, a figure that genuinely warrants the full budgeting exercise in the linked guide rather than a single calculator run.
Reference table for common volumes
| Documents/month (avg. 3 pages) | Pages/month | Monthly cost |
|---|---|---|
| 100 | 300 | €10.50 |
| 1,000 | 3,000 | €105 |
| 10,000 | 30,000 | €1,050 |
| 100,000 | 300,000 | €10,500 |
| 1,000,000 | 3,000,000 | €105,000 |
Sanity-checking the result by hand
Because the formula is one multiplication chained after another, it's worth being able to reproduce the calculator's output on a scrap of paper — a useful habit before presenting any figure to someone else, and a quick way to catch a typo in your own inputs rather than the tool itself. Take 12,500 pages a month as an example: €0.035 × 12,500 is the same as 3.5 cents × 12,500, which is 3.5 × 125 = 437.5, so €437.50. The calculator above will show exactly that for 5,000 documents at 2.5 average pages.
A quick mental shortcut that holds up well: €0.035 per page is very close to €35 per thousand pages, and €35,000 per million pages. Rounding your own page volume to the nearest thousand or million and multiplying by 35 gets you within a percent or two of the exact figure — close enough for a first gut check in a meeting, before pulling up the calculator for the precise number.
Common mistakes when using a calculator like this one
Entering total pages as "documents"
If you already have a total page count rather than a document count, set documents to that figure and average pages to 1 — entering a page count into the documents field and leaving average pages at a default will double-count.
Using a single average across a genuinely mixed document set
If your pipeline processes both 1-page receipts and 20-page reports in meaningfully different volumes, run the calculator once per document type and sum the results rather than blending them into one misleading average.
Treating the output as inclusive of a planning buffer
This tool shows the exact baseline cost for the volume entered — it doesn't add any margin for estimation error or testing overhead, which the budgeting guide covers separately.
Forgetting to update the inputs as real data arrives
An estimate entered before launch is a starting point, not a fixed truth — re-running the calculator with real GET /usage-derived figures once available tightens the number considerably.
Verifying the number live, from the API itself
The calculator above reads the same rate constant this page's source code does — but if you want to confirm it independently, a free API key and one call return the live figure directly.
curl https://flowparse.io/api/v1/usage \
-H "Authorization: Bearer pf_live_xxx"
# → { "plan":"FREE", "pricePerPageEur":0.035, ... }Derived figures worth having alongside the monthly total
| Metric | How to derive it | Why it's useful |
|---|---|---|
| Cost per document | Monthly cost ÷ documents per month | Useful for pricing your own product on top, per document handled |
| Annualized cost | Monthly cost × 12 | The figure most finance approvals actually run on |
| Cost as % of a per-document revenue line | Cost per document ÷ your own average revenue per document | A quick gut check on whether extraction cost is a meaningful share of unit economics |
| Cost per 1,000 pages | Rate × 1,000 — always €35 at the current flat rate | A round, easy-to-remember reference figure for quick mental math |
None of these require a different tool — each is one more arithmetic step on top of the same pages-times-rate output this calculator already produces, worth keeping in your own notes once you've settled on a baseline monthly figure.
Replicating this formula in a spreadsheet
For a budget that needs to live in a shared spreadsheet rather than a browser tab, the same formula translates directly into one cell: with documents per month in cell A1 and average pages per document in A2, the monthly cost is =A1*A2*0.035. Labeling the rate itself in its own cell — rather than typing 0.035 directly into the formula — makes it a one-cell update if the published rate is ever revised, the same defensive pattern this cluster's other pages recommend for a real API integration.
Building a small table with a row per document type, each with its own documents-per-month and average-pages columns, and a total row summing each row's cost, mirrors exactly what the budgeting guide's worked examples show — the calculator above is the fast, single-scenario version of that same spreadsheet.
Why this doesn't need a lookup table
A calculator for a complexity-tiered or credit-based vendor typically needs a lookup table or a set of dropdown assumptions baked in, because the actual rate applied depends on something the calculator can't know in advance — how "complex" a typical document will be judged, or what the current credit-to-page conversion happens to be. This calculator needs neither, because the rate itself doesn't depend on anything but the page count you supply.
What to do once you have a number
A single monthly figure from this calculator is a good starting point, not a finished budget. The budgeting guide in this cluster covers adding a reasonable buffer, comparing against building your own pipeline, and modeling growth scenarios on top of this baseline number.
Who this is for
A developer sizing a first integration
A quick sense of whether a pilot's expected volume fits comfortably inside a free plan or needs a paid one.
A finance reviewer sanity-checking a proposed spend
An independent, exact figure to compare against a number presented by an engineering or product team.
A technical buyer comparing vendors
A concrete monthly figure to place next to another vendor's own quoted pricing.
A team modeling several growth scenarios
Re-run the calculator at different documents-per-month figures to see how the total scales.
A note on estimate accuracy
The calculation itself is exact — given the two inputs, the output is arithmetically correct, not an approximation. The only source of error is in the inputs themselves: an average-pages figure pulled from intuition rather than a real document sample, or a documents-per-month projection that doesn't yet reflect real usage. Revisiting both inputs periodically against actual data, once available from GET /usage, is the most reliable way to tighten the estimate over time.
Using this at very high volume
The calculator handles a volume of a few hundred documents and a volume of tens of millions the same way — the formula doesn't change shape at any input size, which is itself a direct demonstration of the flat rate's core property: there's no volume threshold where the math gets more complicated or a different rate kicks in.
At the higher end of the documents-per-month input, treat the output as a starting figure for the fuller exercise in the budgeting guide rather than a final answer on its own — very large volumes are exactly where a buffer, a growth projection, and a genuine build-vs-buy comparison start to matter more than a single baseline number, even though that baseline number is still exactly correct as far as it goes.
When a calculator like this isn't enough on its own
A single monthly figure is the right tool for a quick estimate or a first gut check, but it deliberately leaves out anything that depends on judgment rather than arithmetic — how much buffer to add, whether building in-house changes the picture, how a growth trajectory should shape a multi-year number. Those questions have real, worked answers elsewhere in this cluster, specifically so this calculator can stay simple rather than growing into a form with a dozen fields trying to cover every possible scenario at once. Start here for the number; move to the guide or the scenario page once the number needs a story behind it, a buffer on top, or a comparison against building the same capability in-house — this page answers only the first, narrowest question well.
Get your API key
Once you have a number you trust, a free API key lets you confirm it against a real extraction call — no credit card required to see the response and its price object.
Security and privacy
This calculator runs entirely in your browser — nothing you enter here is transmitted or stored.
Uploads to the API are encrypted with TLS from end to end.
Processing runs on infrastructure with SOC 2-aligned controls.
Original documents are deleted shortly after processing.
Full details are on the security page.