# USPS API: Estimate postage > Estimates domestic USPS Post Office retail postage between two ZIP Codes for a letter, large envelope, package or flat-rate packaging, by weight and mailing date. Media Mail is left out; a zero-weight letter counts as one ounce. Prices are retail, cheapest first, with each service's estimated delivery. Unofficial. Not affiliated with or endorsed by USPS. - Page: https://fous.com/methods/usps.com/estimate-postage - Method: `usps.com/estimate_postage`, version 1 - Website: usps.com - Returns: services (name, retail price in USD, estimated delivery time and date, included extras, USPS page link), note - Effect: read (it gets data and changes nothing) - Sign-in: none needed - Cost: 1 credit per completed run (1¢ with pay as you go); failed runs are free - Verified: Nov 2, 2026 ## Inputs | Field | Type | Required | In the run below | Description | |---|---|---|---|---| | `width_in` | number | no | | Package width in inches, for example 6; defaults to a small box. Default 6. | | `height_in` | number | no | | Package height in inches, for example 4; defaults to a small box. Default 4. | | `length_in` | number | no | | Package length in inches, for example 8; defaults to a small box. Default 8. | | `ship_date` | string | no | | Planned mailing date in YYYY-MM-DD, for example 2026-10-01; defaults to today (New York time). | | `weight_lb` | number | yes | `2` | Weight in pounds, for example 2; enter 0 for a letter under a pound. | | `weight_oz` | number | no | | Additional ounces beyond the whole pounds, for example 8. Default 0. | | `origin_zip` | string | yes | `"60601"` | Five-digit ZIP Code where the item is mailed, for example 10001. | | `package_type` | string | no | `"flat_rate_box"` | Mailpiece or USPS flat-rate packaging type, for example package. One of "letter", "large_envelope", "package", "flat_rate_envelope", "flat_rate_box". Default "package". | | `destination_zip` | string | yes | `"90001"` | Five-digit destination ZIP Code, for example 94105. | ## Output From a run on Oct 31, 2026. Its input: ```json { "weight_lb": 2, "origin_zip": "60601", "package_type": "flat_rate_box", "destination_zip": "90001" } ``` Its output: ```json { "note": null, "services": [ { "currency": "USD", "page_link": "https://postcalc.usps.com/Calculator/ExtraServices?country=0&ccode=US&oz=60601&omil=False&dz=90001&dmil=False&retail=False&mdt=9/28/2026&mdz=8:00 AM&m=12&hscode=False&p=2&o=0&rect=True&l=0&h=0&w=0&g=0&mt=14&dok=XX&pt=r", "retail_price": 13.65, "service_name": "Priority Mail Small Flat Rate Box", "included_extras": [ "USPS Tracking", "Insurance up to $100" ], "expected_delivery_date": "2026-10-01", "estimated_delivery_time": "Thu, Oct 1" }, { "currency": "USD", "page_link": "https://postcalc.usps.com/Calculator/ExtraServices?country=0&ccode=US&oz=60601&omil=False&dz=90001&dmil=False&retail=False&mdt=9/28/2026&mdz=8:00 AM&m=12&hscode=False&p=2&o=0&rect=True&l=0&h=0&w=0&g=0&mt=13&dok=XX&pt=r", "retail_price": 24.8, "service_name": "Priority Mail Medium Flat Rate Box", "included_extras": [ "USPS Tracking", "Insurance up to $100" ], "expected_delivery_date": "2026-10-01", "estimated_delivery_time": "Thu, Oct 1" }, { "currency": "USD", "page_link": "https://postcalc.usps.com/Calculator/ExtraServices?country=0&ccode=US&oz=60601&omil=False&dz=90001&dmil=False&retail=False&mdt=9/28/2026&mdz=8:00 AM&m=12&hscode=False&p=2&o=0&rect=True&l=0&h=0&w=0&g=0&mt=12&dok=XX&pt=r", "retail_price": 34, "service_name": "Priority Mail Large Flat Rate Box", "included_extras": [ "USPS Tracking", "Insurance up to $100" ], "expected_delivery_date": "2026-10-01", "estimated_delivery_time": "Thu, Oct 1" } ] } ``` ## Run it From code, with a Fous API key in `FOUS_API_KEY`; the answer's `data` holds the output: ```bash curl https://api.fous.com/v1/runs \ -H "Authorization: Bearer $FOUS_API_KEY" \ -H "Content-Type: application/json" \ -d '{"method":"usps.com/estimate_postage","input":{"weight_lb":2,"origin_zip":"60601","package_type":"flat_rate_box","destination_zip":"90001"}}' ``` From an AI agent connected to the Fous MCP server: its `run` with the same method and input. To connect one, give it `set up https://fous.com/SKILL.md`. ## Ask your agent - How much would it cost to mail a 3 lb 4 oz box measuring 12x10x6 inches from ZIP 60614 to 33139 next Tuesday? Show me the cheapest options and delivery dates. - What's the USPS retail price to send a regular letter from 02139 to 98101, and how long will it take? - I'm shipping a flat rate box from Austin 78704 to Denver 80202 on 2026-11-16 — what are my service options and prices on usps.com? - Compare postage for a large envelope weighing 6 ounces going from 30309 to 10011, mailed on December 3rd. - Check usps.com for the cheapest way to ship a 15 lb package (18x14x10) from 85004 to 04101 and when it would arrive. ## Input schema ```json { "type": "object", "required": [ "origin_zip", "destination_zip", "weight_lb" ], "properties": { "width_in": { "type": "number", "default": 6, "description": "Package width in inches, for example 6; defaults to a small box." }, "height_in": { "type": "number", "default": 4, "description": "Package height in inches, for example 4; defaults to a small box." }, "length_in": { "type": "number", "default": 8, "description": "Package length in inches, for example 8; defaults to a small box." }, "ship_date": { "type": "string", "description": "Planned mailing date in YYYY-MM-DD, for example 2026-10-01; defaults to today (New York time)." }, "weight_lb": { "type": "number", "minimum": 0, "description": "Weight in pounds, for example 2; enter 0 for a letter under a pound." }, "weight_oz": { "type": "number", "default": 0, "minimum": 0, "description": "Additional ounces beyond the whole pounds, for example 8." }, "origin_zip": { "type": "string", "maxLength": 5, "minLength": 5, "description": "Five-digit ZIP Code where the item is mailed, for example 10001." }, "package_type": { "enum": [ "letter", "large_envelope", "package", "flat_rate_envelope", "flat_rate_box" ], "type": "string", "default": "package", "description": "Mailpiece or USPS flat-rate packaging type, for example package." }, "destination_zip": { "type": "string", "maxLength": 5, "minLength": 5, "description": "Five-digit destination ZIP Code, for example 94105." } } } ``` ## Output schema ```json { "type": "object", "required": [ "services", "note" ], "properties": { "note": { "type": [ "string", "null" ] }, "services": { "type": "array", "items": { "type": "object", "required": [ "service_name", "retail_price", "currency", "estimated_delivery_time", "expected_delivery_date", "included_extras", "page_link" ], "properties": { "currency": { "type": "string" }, "page_link": { "type": "string" }, "retail_price": { "type": "number" }, "service_name": { "type": "string" }, "included_extras": { "type": "array", "items": { "type": "string" } }, "expected_delivery_date": { "type": [ "string", "null" ] }, "estimated_delivery_time": { "type": [ "string", "null" ] } } }, "description": "Available retail postage options, cheapest first." } } } ``` ## See more - [UPS API: Track package](https://fous.com/methods/ups.com/track-package.md): Tracks a UPS package by tracking number, with its status, delivery details and shipment history when available. - [Zippopotam.us API: Get postal code](https://fous.com/methods/zippopotam.us/get-postal-code.md): Looks up the places, regions and coordinates for a postal code in a supported country on Zippopotam.us. - [Zippopotam.us API: Search postal codes](https://fous.com/methods/zippopotam.us/search-postal-codes.md): Finds postal codes, place names and coordinates for a town and state or region in a country covered by Zippopotam.us. - [Instacart API: Search store products](https://fous.com/methods/instacart.com/search-products.md): Searches a named Instacart store's guest-visible grocery products for a US ZIP code. Prices are in USD and can differ from in-store prices; stock estimates can change. - [Cost Plus Drugs API: Get drug price](https://fous.com/methods/costplusdrugs.com/get-drug-price.md): Looks up a medicine at Cost Plus Drugs by generic or brand name and returns the listed price and its breakdown for a strength, form and quantity, with the strengths and forms on offer. The drug price excludes shipping and taxes; standard shipping is shown separately. - [Drugs.com API: Get drug prices](https://fous.com/methods/drugs.com/get-drug-prices.md): Gets the US cash prices Drugs.com lists for a brand or generic medicine by strength, dosage form and quantity, optionally filtered. Where a range is listed the lower price is returned. - [Realtor.com API: Get home details](https://fous.com/methods/realtor.com/get-home.md): Gets a home's details from Realtor.com by street address or Realtor.com property link: status, list price, value estimate, beds, baths, size, year built, HOA fee, property and tax history, nearby schools, flood risk and photos. - [OfferUp API: Search listings](https://fous.com/methods/offerup.com/search-listings.md): Finds OfferUp items for sale near a US city or ZIP code, with prices, condition, seller names, distance and links. Distances use approximate listing locations.