# Inflation Calculator API > Inflation-economics maths as an API, computed locally and deterministically. The adjust endpoint expresses a value across time in two ways — by an annual inflation rate over a number of years, V = amount·(1+r)^years, or by a ratio of consumer-price-index figures, V = amount·CPI_end/CPI_start — so an old price can be restated in today's money, with the total inflation over the period. The real-rate endpoint computes the real (inflation-adjusted) interest or investment rate from a nominal rate and an inflation rate using the Fisher equation, 1 + real = (1 + nominal)/(1 + inflation), alongside the rough nominal-minus-inflation approximation. The purchasing-power endpoint shows how inflation erodes money over time — the future buying power of today's amount, amount/(1+r)^years, the value lost and the larger amount needed to maintain the same purchasing power. Rates may be entered as a percent or a fraction and amounts in any currency. Everything is computed locally and deterministically, so it is instant and private. Ideal for personal-finance, budgeting, salary, retirement-planning and economics app developers, cost-of-living and real-return tools, and finance education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is inflation adjustment; for loan repayments use a loan API and for investment growth an investment API. ## Authentication All requests require your oanor API key in the `x-oanor-key` header. Get one at https://www.oanor.com/developer/keys. ```bash curl -H "x-oanor-key: oanor_live_…" "https://api.oanor.com/inflation-api/..." ``` ## Pricing - **Free** (Free) — 2,800 calls/Mo, 2 req/s - **Starter** ($13/Mo) — 35,000 calls/Mo, 6 req/s - **Pro** ($34/Mo) — 215,000 calls/Mo, 15 req/s - **Mega** ($99/Mo) — 1,400,000 calls/Mo, 40 req/s ## Endpoints ### Inflation #### `GET /v1/adjust` — Inflation adjust **Parameters:** - `amount` (query, required, string) — Amount Example: `100` - `rate` (query, optional, string) — Annual inflation rate (% or fraction) Example: `3` - `years` (query, optional, string) — Number of years Example: `10` - `cpi_start` (query, optional, string) — CPI at start - `cpi_end` (query, optional, string) — CPI at end **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/inflation-api/v1/adjust?amount=100&rate=3&years=10" ``` **Response:** ```json { "data": { "note": "Annual-rate method: adjusted = amount · (1+r)^years. The rate may be a percent (3) or a fraction (0.03).", "inputs": { "rate": 3, "years": 10, "amount": 100 }, "method": "annual-rate", "adjusted_amount": 134.3916, "inflation_factor": 1.34391638, "total_inflation_pct": 34.391638 }, "meta": { "timestamp": "2026-06-05T11:30:32.383Z", "request_id": "d49ccc26-e12f-4518-9813-04ce2957c52c" }, "status": "ok", "message": "Inflation adjust", "success": true } ``` #### `GET /v1/purchasing-power` — Purchasing power **Parameters:** - `amount` (query, required, string) — Amount Example: `100` - `rate` (query, required, string) — Inflation rate (% or fraction) Example: `3` - `years` (query, required, string) — Number of years Example: `10` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/inflation-api/v1/purchasing-power?amount=100&rate=3&years=10" ``` **Response:** ```json { "data": { "note": "After 'years' of inflation, today's amount buys future_purchasing_power = amount/(1+r)^years; amount_to_maintain_power = amount·(1+r)^years keeps the same buying power.", "inputs": { "rate": 3, "years": 10, "amount": 100 }, "value_lost": 25.5906, "erosion_pct": 25.590609, "future_purchasing_power": 74.4094, "amount_to_maintain_power": 134.3916 }, "meta": { "timestamp": "2026-06-05T11:30:32.470Z", "request_id": "f45b8664-6007-47ef-bf35-19377ae34b79" }, "status": "ok", "message": "Purchasing power", "success": true } ``` #### `GET /v1/real-rate` — Fisher real rate **Parameters:** - `nominal_rate` (query, required, string) — Nominal rate (% or fraction) Example: `7` - `inflation_rate` (query, required, string) — Inflation rate (% or fraction) Example: `3` **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/inflation-api/v1/real-rate?nominal_rate=7&inflation_rate=3" ``` **Response:** ```json { "data": { "note": "Fisher equation: 1 + real = (1 + nominal)/(1 + inflation). The approximate form (nominal − inflation) is only accurate at low rates.", "inputs": { "nominal_rate": 7, "inflation_rate": 3 }, "real_rate": 0.03883495, "real_rate_pct": 3.883495, "approximate_real_rate_pct": 4 }, "meta": { "timestamp": "2026-06-05T11:30:32.575Z", "request_id": "2cafd0ce-4f2e-43e2-9149-2757b764bda7" }, "status": "ok", "message": "Fisher real rate", "success": true } ``` ### Meta #### `GET /v1/meta` — Spec **Example:** ```bash curl -H "x-oanor-key: $KEY" \ "https://api.oanor.com/inflation-api/v1/meta" ``` **Response:** ```json { "data": { "notes": "Rates may be a percent (3) or a fraction (0.03). Amounts are in any currency. CPI values are index numbers.", "service": "inflation-api", "formulae": { "fisher": "1 + real = (1 + nominal)/(1 + inflation)", "adjust_cpi": "V = amount · CPI_end / CPI_start", "adjust_rate": "V = amount · (1+r)^years", "purchasing_power": "P = amount / (1+r)^years" }, "endpoints": { "GET /v1/meta": "This document.", "GET /v1/adjust": "Adjust an amount for inflation by an annual rate over n years, or by CPI start/end.", "GET /v1/real-rate": "Real (inflation-adjusted) interest rate from nominal rate and inflation (Fisher).", "GET /v1/purchasing-power": "Future purchasing power and the amount needed to keep buying power." }, "description": "Inflation calculator: adjust a value across years by an annual rate or a CPI ratio, the Fisher real interest rate, and the erosion of purchasing power over time." }, "meta": { "timestamp": "2026-06-05T11:30:32.688Z", "request_id": "580ccbfb-0565-4df0-8a51-12e8cf899d62" }, "status": "ok", "message": "Meta", "success": true } ``` --- Marketplace page: https://www.oanor.com/api/inflation-api OpenAPI spec: https://www.oanor.com/api/inflation-api/openapi.json