Iso Paper

{
  "areaSquareMeters": 0.06237,
  "asOf": "2026-10-12T01:48:14.409Z",
  "aspectRatio": 1.4143,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "heightInches": 11.693,
  "heightMm": 297,
  "heightPoints": 841.9,
  "name": "A4",
  "nextLarger": {
    "height": 420,
    "name": "A3",
    "width": 297
  },
  "nextSmaller": {
    "height": 210,
    "name": "A5",
    "width": 148
  },
  "notChecked": [
    "tolerances on trimmed paper (ISO allows about +/-1.5 mm on small sizes)",
    "the Japanese JIS B series, which is different from ISO B",
    "…1 more"
  ],
  "reasons": [
    "Every size is half the area of the one before, with the same 1:1.414 ratio.",
    "A0 has an area of one square metre."
  ],
  "source": "computed locally (ISO 216: halve the longer side and round down to a whole mm)",
  "summary": "A4 is 210 x 297 mm (8.27 x 11.69 in).",
  "verdict": "COMPUTED",
  "widthInches": 8.268,
  "widthMm": 210,
  "widthPoints": 595.3
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://paper-print-calc.x402tookit.com/iso-paper?series=A&size=4'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://paper-print-calc.x402tookit.com/iso-paper?series=A&size=4' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fpaper-print-calc.x402tookit.com%2Fiso-paper
const res = await pay("https://paper-print-calc.x402tookit.com/iso-paper?series=A&size=4");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://paper-print-calc.x402tookit.com/iso-paper?series=A&size=4")
    print(res.status_code, res.text)