How do I use the cable sizing calculator?

Enter your design inputs below and click Calculate. The tool applies UK building services methods for cable sizing and reports results with assumptions.

What standard applies to cable sizing?

Confirm the relevant British Standard or Approved Document on your project. This calculator is for first-pass sizing — verify against the issued specification before sign-off.

Can I save cable sizing results in BuildFlo?

Sign up for a free BuildFlo account to save calculation results in your project workspace and attach them to your calculation folder.

BuildFlo Design Guide · Electrical · Electrical

cable sizing calculator for UK building services

Recommend live CSA and MCB from Ib, length and installation method. Free UK cable sizing calculator with electrical guidance.

What this calculator does

Cable sizing helps UK building services engineers with recommend live csa and mcb from ib, length and installation method. The calculation follows Electrical methods used in everyday MEP design — enter your project inputs below for a first-pass result.

Whether you searched for "cable sizing", "cable sizing calculator", or "how to cable size", this page gives you a working tool plus the context to use it on a real job.

When to use it

Use this for early-stage sizing and sanity checks on UK building services work. It is not a substitute for issued calculations — verify against the project specification, drawings, and relevant standard before sign-off.

How to use it

1. Fill in the inputs for your scenario (defaults are starting points only). 2. Click Calculate — results include the method and assumptions where applicable. 3. Verify against the project specification and relevant standard before issuing.

Typical output unit: mm².

Tips

Defaults are indicative — replace with project-specific values from the architect, structural, or MEP spec.
For issued calculations, save results in your BuildFlo project and attach to the calculation folder.
Need the regulation citation? Open BuildFlo chat in the app and ask about cable sizing under UK standards.

---

*Sign up for BuildFlo for the full calculator suite, saved results, and project workspace.*

Frequently asked questions

How do I use the cable sizing calculator?: Enter your design inputs below and click Calculate. The tool applies UK building services methods for cable sizing and reports results with assumptions.
What standard applies to cable sizing?: Confirm the relevant British Standard or Approved Document on your project. This calculator is for first-pass sizing — verify against the issued specification before sign-off.
Can I save cable sizing results in BuildFlo?: Sign up for a free BuildFlo account to save calculation results in your project workspace and attach them to your calculation folder.