TakeoffMetric Construction Calculators

takeoffmetric-mcp

A Model Context Protocol server (stdio) that runs the construction calculators of TakeoffMetric (https://takeoffmetric.com/) from an MCP client. It ships 15 calculators, a tool that lists them, and a search over a table of estimating constants in which every row names its published source.

The calculators are not re-implemented here. The site's TypeScript engine is bundled unchanged into vendor/engine.mjs, and the test suite checks that each tool returns what the engine source computes.

Install

Requires Node.js 20 or later.

npx -y takeoffmetric-mcp

Claude Desktop (claude_desktop_config.json):

{  "mcpServers": {    "takeoffmetric": {      "command": "npx",      "args": ["-y", "takeoffmetric-mcp"]    }  }}

Claude Code:

claude mcp add takeoffmetric -- npx -y takeoffmetric-mcp

Tools

Two more tools complete the server:

• list_calculators: tool name, title, page URL, one-line description and input keys of each calculator.
• search_constants: rows of the constants table matched by a substring (query) and/or a category, 50 rows at most per call.

Inputs

Each calculator's input schema is generated at start-up from the engine's own input list, so keys, bounds, options and defaults are the ones of the matching form on the site.

• Every input is optional. A key you leave out takes the engine default, as an untouched form field does.
• system is "imperial" (default) or "metric". It sets the unit the numbers are typed in and the defaults.
• A length is a number in the unit named in its description, or a string that carries its unit, such as "20 ft 6 in".
• An unknown key or an out-of-range value returns isError: true with one message per field. Nothing is computed from a clamped value.

Output

A JSON text block: calculator, url, system, engine_version, revised, inputs_used, primary, secondary, takeoff, warnings, assumptions. inputs_used is the engine's normalized input (lengths in metres). assumptions lists what the result rests on, and warnings carries the cautions the page would show.

Worked example

Request (tools/call, tool calc_concrete_slab):

{"length":24,"width":16,"thickness":"5 in","price":165}

Response, copied from a run of this server (whitespace condensed):

{  "calculator": "calc_concrete_slab",  "url": "https://takeoffmetric.com/concrete/concrete-calculator/",  "system": "imperial",  "engine_version": "1.2.0",  "revised": "2026-09-19",  "inputs_used": {"system":"imperial","sections":[{"length":7.315200000000001,"width":4.8768},{"length":0,"width":0},{"length":0,"width":0}],"thickness":0.127,"wastePct":10,"bagSize":"60","pricePerCuYd":165,"thickenedEdge":false,"edgeDepth":0.30479999999999996,"edgeWidth":0.30479999999999996,"gravelDepth":0.1016,"unitWeight":150,"truckCuYd":10,"minLoadCuYd":null,"shortLoadFee":null},  "primary": {"value":6.52,"unit":"cuyd","label":"Concrete volume","precision":2},  "secondary": [    {"value":6.75,"unit":"cuyd","label":"Order quantity","precision":2},    {"value":176,"unit":"cuft","label":"Concrete volume","precision":1},    {"value":384,"unit":"sqft","label":"Slab area","precision":0},    {"value":26400,"unit":"lb","label":"Concrete weight","precision":0},    {"value":392,"unit":"bag","label":"60 lb bags","precision":0},    {"value":1,"unit":"load","label":"Truck loads","precision":0},    {"value":10,"unit":"ft","label":"Control-joint spacing","display":"10'-0″ to 15'-0″"},    {"value":1113.75,"unit":"usd","label":"Estimated concrete cost","precision":2}  ],  "takeoff": [    {"key":"readymix","item":"Ready-mix concrete","qty":5.93,"unit":"cuyd","waste":10,"order":6.75,"orderUnit":"cuyd","note":"Rounded up to the nearest 0.25 cu yd."},    …    {"key":"trucks","item":"Ready-mix truck loads","qty":6.52,"unit":"cuyd","order":1,"orderUnit":"load","note":"10 cu yd per load (your assumption)."},    {"key":"gravel","item":"Compacted base, 4″","qty":4.74,"unit":"cuyd","order":6.5,"orderUnit":"cuyd","note":"Loose volume ordered = compacted volume x 1.31 (3,570 / 2,730 lb/cu yd, FHWA Exhibit 5.1 A, gravel dry, average gradation; 1.17 uniformly graded, 1.49 well graded). For estimating purposes, ±33%: a highway embankment, not a plate-compacted base."},    {"key":"cost","item":"Concrete cost at your price","qty":6.75,"unit":"cuyd","order":1113.75,"orderUnit":"usd","note":"6.75 cu yd x $165.00 / cu yd."}  ],  "warnings": [    {"level":"caution","code":"too-many-bags","message":"392 bags is a day of mixing. Price a ready-mix delivery instead."}  ],  "assumptions": [    "Volume = length x width x thickness; 1 cubic yard = 27 cubic feet.",    "Waste allowance 10% applied to the net volume.",    "Ready-mix rounded up to 0.25 cu yd; truck capacity 10 cu yd (editable).",    …    "Unit weight 150 lb/cu ft (editable; normal-weight concrete runs about 140-155).",    "Contraction joints at 24-36 times the slab thickness, capped at 15 ft (NRMCA CIP 6).",    "Thickness, reinforcement and base depth come from your drawings or local code."  ]}

How the numbers are sourced

• Formulas, constants and rounding rules come from the engine bundle. vendor/ENGINE_COMMIT.txt records the commit it was built from, and every response carries the calculator's engine_version and revised date.
• Each tool computes with the same engine as its page on the site. calc_gravel, for instance, runs the engine behind https://takeoffmetric.com/earthwork/gravel-calculator/.
• search_constants reads vendor/constants.csv (dataset 1.1.0, 148 rows). Each row gives the value, its unit, the SI value, the condition it applies to, and the publisher, title and URL of the document it was read from. 55 rows carry no value because their publishers do not allow republication: they return value: null, values_withheld: true, the publisher's domains in withheld_hosts, and the URL where the value can be read.
• The site's methodology (tested formulas, assumptions shown on the page, sources as documents, versioned sheets) is at https://takeoffmetric.com/methodology/.

Limits

• Results are estimates. Confirm quantities with your plans, your supplier and your local code before ordering or building.
• This release covers 15 calculators. Calculators that apply building-code provisions, or that rely on third-party tables the site links to without reproducing them, are not part of it.
• Responses carry numbers and notes only: no drawing and no CSV export.
• unit fields use the engine's unit codes. Several results that are not plain counts are coded ea; read label and display for their meaning.
• Prices are whatever you type in. The server holds no price data and makes no network request.
• Transport is stdio only.

Development

npm installnpm test

The tests run with this repository alone. npm run sync-engine and npm run make-fixtures are maintainer scripts: they rebuild vendor/ and test/fixtures.json from the site's source repository, which users of the package never need.

License

Server code: MIT. Calculation engine (vendor/engine.mjs): copyright TakeoffMetric, distributed with this package to run as part of it, not licensed for modification or separate redistribution. Both are set out in LICENSE. Constants table: CC BY 4.0 for the compilation; federal values are public domain; any other value stays under its publisher's terms. See DATA_LICENSE.md.