Public API sandbox

Calculator scenario tester

Use realistic lending scenarios, submit requests directly to the API, and review the live JSON responses without signing in.

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Single-rate calculation

Test the standard annuity endpoint with a flat interest profile.

Credit value
Interest rate (%)
Months
Account fee
Processing fee
Rescheduling amount
Voucher code
JSONP callback (optional)
Existing customer
Business loan
Self-employed
No request submitted yet.

Monthly payment

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APR

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Total repayment

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{}

Calculation math

Run a request to see the formula and substituted values.

Two-phase mortgage

Submit a two-period mortgage scenario and inspect the repayment transition.

Credit value
Account fee
Processing fee
First rate (%)
First period months
Second rate (%)
Second period months
JSONP callback (optional)
Existing customer
Genossenschaftswohnung
No request submitted yet.

First payment

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Second payment

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APR

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Total repayment

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{}

Calculation math

Run a request to see the formula and substituted values.

Feasibility planner

Calculate the maximum property price based on your net income and available equity.

Percentage factors accept either normalized decimals (for example 0.55) or whole percentages (for example 55).

Monthly net income
Own equity
Duration (years)
Reduced monthly rate (optional)
Monthly rate slider

After the first calculation, adjust the slider to send a reduced monthly rate back to the API.

Selected rate: 0.00

Adjustable factors (Optional)
DSTI (55 or 0.55)
Fictional rate (5.07 or 0.0507)
Actual rate (2.65 or 0.0265)
Purchase costs (10 or 0.10)
Loan costs (2 or 0.02)
No request submitted yet.

Max Property Price (Excl. Costs)

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Max Monthly Rate

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Total Available Funds

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{}
Public API documentation

This section describes the public calculator endpoints, required payload fields, optional fee overrides, and the active validation boundaries enforced by the backend. GET is the preferred transport for the calculator endpoints, while POST remains available for compatibility.

Global limits

Maximum credit value: 10,000,000

Retention unit: months

Rates and fees must be zero or greater.

GET /api/calculate-rate

Calculates a single monthly annuity payment, APR, fee totals, and repayment summary for a flat-rate loan.

Required

credit_value

Loan principal. Numeric, minimum 1, maximum 10,000,000.

retention

Loan term in months. Integer, minimum 1.

interest_rate

Annual interest rate for the whole loan. Numeric, minimum 0.

callback

Optional JSONP callback. Must begin with a letter, underscore, or dollar sign.

GET /api/calculate-mortgage-periods

Calculates a two-phase mortgage with a first-rate period, remaining debt handover, second payment, APR, and total repayment.

Required

credit_value

Loan principal. Numeric, minimum 1, maximum 10,000,000.

retention

Total loan term in months. Integer, minimum 1.

interest_rate_1

First annual interest rate. Numeric, minimum 0.

interest_rate_2

Second annual interest rate. Numeric, minimum 0.

interest_period_1

Length of the first rate period in months. Integer, minimum 1, and it must not exceed retention.

GET /api/calculate-feasibility

Computes the maximum financeable property price from net income, equity, and term, with optional adjustable factors.

Required

income

Monthly net income. Numeric, minimum 0.

equity

Available own equity. Numeric, minimum 0.

duration

Desired loan duration in years. Integer, minimum 1.

reduced_rate

Optional reduced monthly rate to recalculate the affordability ceiling.

Optional fee overrides

  • processingFee: Fixed setup fee override. Numeric, minimum 0.
  • entryFeePerc: Entry fee percentage override. Numeric, minimum 0.
  • riskFeePerc: Risk fee percentage override. Numeric, minimum 0.
  • estimateFee: Fixed valuation fee override. Numeric, minimum 0.
  • estimateFeePerc: Valuation fee percentage override. Numeric, minimum 0.
  • accountFee: Monthly account fee override. Numeric, minimum 0.

Response behavior

  • Successful responses return status and data payloads with payment, APR, fee, and repayment information.
  • Validation failures return HTTP 422 with a structured errors object.
  • JSONP is supported when a valid callback is supplied.
  • Settings are read-only on the public endpoint and reflect the active server configuration.

Operational limitations

  • All periods are expressed in months.
  • Negative rates and negative fees are rejected by validation.
  • The first mortgage period cannot be longer than the total retention.
  • Requests above the configured maximum credit value are rejected.

Cross-origin requests (CORS)

  • Parameters may be sent as form-encoded fields, a query string, or JSON — the payload is identical.
  • Cross-origin browser callers should use a CORS simple request: a form-encoded body or GET query, with no custom headers and no application/json content type.
  • This avoids the OPTIONS preflight, which the upstream WAF rejects with a 403 (seen in the browser as a missing Access-Control-Allow-Origin header).
  • Allowed origins are configured server-side via CORS_ALLOWED_ORIGINS.
Live settings

Read the currently active calculator configuration returned by the API.

Quick checks

  • Confirm fee tiers returned by the backend match business expectations.
  • Verify HTTPS enforcement and IRR parameters after an admin change.
  • Use this panel after management updates to validate persisted overrides.
Settings not loaded yet.

Default account fee

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Maximum credit value

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HTTPS enforcement

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{}