NEC Calculator MCP Server
SparkQuote's free NEC calculators also run as an MCP server, so Claude, ChatGPT and other AI assistants can compute a wire size or look up Table 310.16 instead of answering from memory. Add https://sparkquote.ai/mcp as a remote MCP server. There is no account, API key or configuration.
Server details
| URL | https://sparkquote.ai/mcp |
|---|---|
| Transport | Streamable HTTP (JSON responses, stateless) |
| Authentication | None |
| Tools | 10, all read-only |
| Code edition | NEC 2023 (NFPA 70) |
| Price | Free |
It is also listed in the official MCP registry as ai.sparkquote/nec-calculators and on Smithery.
Add it to your assistant
Claude (claude.ai and the desktop app). Open Settings → Connectors, choose Add custom connector, name it SparkQuote and paste https://sparkquote.ai/mcp. Leave the OAuth fields empty.
ChatGPT. Custom MCP servers need developer mode: Settings → Apps → Advanced settings → Developer mode. Then create an app with the URL https://sparkquote.ai/mcp and authentication set to none.
Claude Code.
claude mcp add --transport http sparkquote https://sparkquote.ai/mcp
Codex CLI (~/.codex/config.toml):
[mcp_servers.sparkquote]
url = "https://sparkquote.ai/mcp"
Cursor, VS Code and other clients that take a JSON config:
{ "mcpServers": { "sparkquote": { "url": "https://sparkquote.ai/mcp" } } }
Tools
Each tool runs the same code as the calculator page it links to, and every argument has a default, so a tool called with no arguments returns that page's worked example.
| Tool | What it answers | Web version |
|---|---|---|
wire_size | Conductor size for a breaker or load, by ampacity and by voltage drop, plus the equipment ground | Wire size calculator |
nec_ampacity | One Table 310.16 value: material, temperature column and size | Ampacity chart |
voltage_drop | Volts and percent drop for a conductor size, load and one-way length | Voltage drop calculator |
watts_to_amps | Current for a load in watts, single- or three-phase, with the 125% continuous value | Watts to amps |
conduit_fill | Percent fill and the maximum number of THHN/THWN-2 conductors in EMT or PVC | Conduit fill calculator |
box_fill | Minimum box volume from the 314.16(B) allowances | Box fill calculator |
load_calculator | Dwelling service load by the 220.82 optional method | Load calculator |
ohms_law | The other two of volts, amps, ohms and watts from any two | Ohm's law calculator |
panel_schedule | Circuits laid out on a single- or three-phase panel, with load per phase and the imbalance | Panel schedule template |
bid_calculator | Bid price from material, markup, labor, job costs, overhead and a target margin | Bid calculator |
Every result comes back as text plus structured content: a one-line answer, the supporting rows, the inputs that were used (including defaults), the code edition and the link to the calculator page.
Example
Asked "What size copper wire for a 60 A circuit at 240 V, 150 ft away?", the assistant calls wire_size with amps: 60, volts: "240", feet: 150 and gets:
Use 4 AWG copper.
- Smallest for ampacity: 6 AWG (65 A)
- Smallest for voltage drop: 4 AWG (2.3% = 5.6 V)
- Equipment ground (250.122(B), increased with conductors): 6 AWG Cu / 4 AWG Al
Inputs: material=cu, temp=75, amps=60, volts=240, phase=1, feet=150, limit=3
Source: SparkQuote, NEC 2023 (NFPA 70): https://sparkquote.ai/tools/wire-size-calculator
Code minimum under the stated assumptions; check local amendments and the adopted edition.
Invalid input returns an error the assistant can act on. For example, nec_ampacity without a temperature column answers: Use material "cu" or "al", temp "60", "75" or "90", and a listed size such as "12" or "250".
Limits
- Results are code minimums under the stated assumptions. They don't apply ambient temperature correction, adjustment for more than three current-carrying conductors, or local amendments unless the tool says so. Your adopted code edition and the inspector decide.
- The tools calculate. They don't read drawings, look up prices or store anything between calls.
- The server only answers tool calls. It has no resources or prompts and never reads your conversation.
Data and privacy
A tool call sends the server only the tool name and its arguments. For each call we log the tool name, whether it succeeded and the client's user agent (which identifies the assistant, not you) as an anonymous analytics event. Arguments and results are not stored, and no account or personal information is involved. Details are in the privacy policy, and use is covered by the terms of use.
Support
Report a wrong result or a connection problem to privacy@sparkquote.ai with the tool name and the arguments you used. How the calculators are built and checked: how we build our calculators.
Frequently asked questions
Is the SparkQuote MCP server free?
Yes. There is no account, API key or usage fee.
Does it work with ChatGPT?
Yes, as a custom app in developer mode with the URL https://sparkquote.ai/mcp and no authentication.
Which NEC edition does it use?
NEC 2023 (NFPA 70). Each result names the edition and the table or section it used.
Can the assistant change anything through it?
No. All ten tools are read-only calculations and are marked read-only in their MCP annotations.
Sources
- NFPA 70, National Electrical Code, 2023 edition (NFPA offers free read-only access). Values on this page follow the NEC 2023; check the edition and local amendments your jurisdiction has adopted.
- Tables cited: Table 310.16.
- Sections cited: 250.122(B) and 314.16(B).
- How the numbers are checked: how we build our calculators.