Body Fat Navy

{
  "asOf": "2026-10-11T08:36:49.562Z",
  "bodyFatPct": 17.51,
  "category": "Average",
  "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.",
  "fatMassKg": null,
  "inputsInches": {
    "height": 70,
    "hip": null,
    "neck": 15,
    "waist": 34
  },
  "leanMassKg": null,
  "notChecked": [
    "measurement technique (a 1 cm error moves the result 1 to 2 points)",
    "anything but a rough estimate: the Navy method is accurate to about 3 to 4 points against DEXA and is poor at very low or high body fat and for very muscular people",
    "…2 more"
  ],
  "reasons": [
    "US Navy circumference method (inches, base-10 logs). Accuracy is about 3 to 4 points against DEXA.",
    "Categories are the American Council on Exercise ranges."
  ],
  "sex": "male",
  "source": "computed locally",
  "summary": "Estimated body fat 17.5% (Average).",
  "verdict": "AVERAGE"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://fitness-calc.x402tookit.com/body-fat-navy?height=70&neck=15&sex=male&units=imperial&waist=34'

# 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://fitness-calc.x402tookit.com/body-fat-navy?height=70&neck=15&sex=male&units=imperial&waist=34' \
  | 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%2Ffitness-calc.x402tookit.com%2Fbody-fat-navy
const res = await pay("https://fitness-calc.x402tookit.com/body-fat-navy?height=70&neck=15&sex=male&units=imperial&waist=34");
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://fitness-calc.x402tookit.com/body-fat-navy?height=70&neck=15&sex=male&units=imperial&waist=34")
    print(res.status_code, res.text)