B2B API — Omni Calculator has no API. CalcHub does.

Calculator API for fintechs & developers

10 production-ready financial calculators exposed as a clean JSON API. EMI, SIP, FD, GST, Salary, BMI and more. POST inputs, get results. Free tier available — no credit card required.

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Simple, transparent pricing

Free

100 req/day

✓All 10 calculators
✓JSON responses
✓X-RateLimit-* headers
✓Community support
✓CORS enabled

Get API key (free)

10 calculators, all available via API

Every calculator is a single POST endpoint. Same results as the web UI.

🏦EMI Calculator

curl -X POST https://calccrack.com/api/v1/calc/emi-calculator \
  -H "Content-Type: application/json" \
  -d '{"principal":3000000,"annualRate":8.5,"tenureMonths":240}'

{"calc":"emi-calculator","result":{"emi":26035,"totalInterest":3248362,"totalPayment":6248362}}

📈SIP Calculator

curl -X POST .../api/v1/calc/sip-calculator \
  -d '{"monthlyInvestment":10000,"annualRate":12,"years":20}'

{"result":{"totalInvested":2400000,"estimatedReturns":7494104,"totalValue":9894104}}

🏛️FD Calculator

curl -X POST .../api/v1/calc/fd-calculator \
  -d '{"principal":100000,"annualRate":7,"years":5}'

{"result":{"maturity":141478,"interest":41478}}

💰Compound Interest

curl -X POST .../api/v1/calc/compound-interest \
  -d '{"principal":100000,"annualRate":8,"years":10,"frequency":4}'

{"result":{"amount":221964,"interest":121964}}

💼Salary Calculator

curl -X POST .../api/v1/calc/salary-calculator \
  -d '{"annualCTC":1200000}'

{"result":{"grossMonthly":100000,"monthlyTax":20000,"netMonthly":80000,"annualTax":240000}}

🧾GST Calculator

curl -X POST .../api/v1/calc/gst-calculator \
  -d '{"amount":10000,"gstRate":18,"mode":"add"}'

{"result":{"gstAmount":1800,"total":11800,"baseAmount":10000}}

⚖️BMI Calculator

curl -X POST .../api/v1/calc/bmi-calculator \
  -d '{"weightKg":70,"heightCm":175}'

{"result":{"bmi":22.86,"category":"Normal weight","color":"green"}}

🎂Age Calculator

curl -X POST .../api/v1/calc/age-calculator \
  -d '{"dob":"1990-06-15"}'

{"result":{"years":35,"months":9,"days":21,"totalDays":13079}}

📊Percentage Calculator

curl -X POST .../api/v1/calc/percentage-calculator \
  -d '{"mode":"percent-of","a":15,"b":200}'

{"result":30}

🔄Unit Converter

curl -X POST .../api/v1/calc/unit-converter \
  -d '{"value":1,"from":"Kilometer","to":"Mile","category":"length"}'

{"result":0.6214}

Works with any language

cURL

curl -X POST https://calccrack.com/api/v1/calc/emi-calculator \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ch_YOUR_API_KEY" \
  -d '{
    "principal": 3000000,
    "annualRate": 8.5,
    "tenureMonths": 240
  }'

JavaScript (fetch)

const res = await fetch(
  'https://calccrack.com/api/v1/calc/emi-calculator',
  {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'Authorization': 'Bearer ch_YOUR_API_KEY',
    },
    body: JSON.stringify({
      principal: 3000000,
      annualRate: 8.5,
      tenureMonths: 240,
    }),
  }
);
const { result } = await res.json();
console.log(`EMI: ₹${result.emi.toFixed(0)}/month`);

Python (requests)

import requests

resp = requests.post(
    "https://calccrack.com/api/v1/calc/emi-calculator",
    headers={"Authorization": "Bearer ch_YOUR_API_KEY"},
    json={"principal": 3000000, "annualRate": 8.5, "tenureMonths": 240},
)
result = resp.json()["result"]
print(f"EMI: ₹{result['emi']:.0f}/month")

Go (net/http)

package main

import (
  "bytes"
  "encoding/json"
  "fmt"
  "net/http"
)

func main() {
  body, _ := json.Marshal(map[string]any{
    "principal": 3000000, "annualRate": 8.5, "tenureMonths": 240,
  })
  req, _ := http.NewRequest("POST",
    "https://calccrack.com/api/v1/calc/emi-calculator",
    bytes.NewReader(body))
  req.Header.Set("Content-Type", "application/json")
  req.Header.Set("Authorization", "Bearer ch_YOUR_API_KEY")
  resp, _ := http.DefaultClient.Do(req)
  defer resp.Body.Close()
  var out map[string]any
  json.NewDecoder(resp.Body).Decode(&out)
  fmt.Println(out["result"])
}

What ships on each tier

Feature	Free	Pro	Business	Enterprise
JSON responses	✓	✓	✓	✓
X-RateLimit-* headers	✓	✓	✓	✓
CORS enabled	✓	✓	✓	✓
OpenAPI 3.0 spec	✓	✓	✓	✓
Auto-retry on 429	—	✓	✓	✓
Webhook delivery	—	✓	✓	✓
White-label embeds	—	✓	✓	✓
Priority support	—	✓	✓	✓
Response caching	—	—	✓	✓
Custom rate limits	—	—	✓	✓
Dedicated subdomain	—	—	✓	✓
Multi-region routing	—	—	✓	✓
SLA guarantee	—	—	—	✓
On-prem option	—	—	—	✓
HIPAA-adjacent support	—	—	—	✓

Trusted by fintech teams

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Frequently asked questions

How is billing handled?

Billing is monthly via Stripe. You can upgrade, downgrade, or cancel any time from your dashboard. Prorated refunds on downgrades.

Can I upgrade or downgrade mid-month?

Yes. Upgrades take effect immediately with a prorated charge. Downgrades take effect at the next billing cycle.

What rate limit algorithm do you use?

Fixed window counter: your daily allowance resets at midnight UTC. The X-RateLimit-Reset header gives you the exact Unix timestamp of next reset.

Can I self-host the calculator API?

The calculation logic is MIT-licensed at @calchub/api on npm. You can run the formulas client-side or server-side. The managed API adds rate limiting, monitoring, and a stable URL contract.

Do you store my request data?

No. The API is stateless — inputs are not persisted. We log aggregate request counts per API key for rate limiting and billing only.

What happens when I hit the rate limit?

You receive a 429 Too Many Requests response with X-RateLimit-Remaining: 0 and X-RateLimit-Reset telling you when the window resets.

Ready to build?

Test every endpoint in the interactive playground — no API key required. Get a free key in 30 seconds when you're ready for production.

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