Cable Size Calculator

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Disclaimer
Buckingham Electrical Ltd Cable Size Calculator Disclaimer

This calculator provides recommended cable sizes based on the information input by the user, serving solely as a guideline. The suggested calculations adhere to the BS7671 Requirements for Electrical Installation and IEE Wiring Regulations, focusing on voltage drops at 230 and 400 volts. To offer this guidance, we've made certain assumptions, but it's crucial for users to verify that all data and assumptions align with their specific needs.

The onus of ensuring the suitability and accuracy of any chosen cable for its intended application lies with the user.

For flexible cords, the BS7671 current carrying capacity tables do not cover various installation methods. However, our calculator includes results for flexible cords across all installation methods for user convenience. Users must independently verify the appropriateness of flexible cords for their projects.

In our effort to enhance user experience, we have amalgamated the results for flexible cords into a single output within our calculator. For detailed individual tables and applicable correction factors, please consult the BS7671 guidelines.

Buckingham Electrical Ltd bears no responsibility for the application of the proposed cable sizes or any consequences thereof.

How the cable size calculator works

Cable sizing balances four things: the load (in kW or amps), the supply type (single or three phase), the length of the cable run, and the maximum voltage drop you can accept. UK practice allows up to 5% voltage drop for general circuits and 3% for dedicated circuits — which is why the calculator asks you to choose. Longer runs and higher loads push you toward larger conductor sizes.

If you want the theory behind the tool, we've written about it on the blog: a guide to calculating voltage drop, the difference between a watt and an amp, and the story behind this calculator app.

The results are indicative. Final cable selection must account for installation method, grouping, ambient temperature and protective devices under BS 7671 — talk to our team before you order or install.

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