Planning Tools and Calculators | UK Planning Advice

Make Informed Planning Decisions

Our interactive planning tools are designed to help UK homeowners and developers navigate the planning system with confidence. Whether you need to check if your project qualifies for permitted development, calculate roof volumes for a loft conversion, or estimate the impact of an extension, our tools provide clear guidance based on current regulations.

Important to Know

While our tools provide guidance based on current planning regulations, they should not replace professional advice for complex projects. Always check with your local planning authority if you're unsure about your specific situation.

Our Planning Tools

Below you'll find our collection of interactive planning tools to help with various aspects of the planning process:

Permitted Development Checker

Answer a series of simple questions to determine if your project is likely to fall under permitted development rights or whether you'll need to apply for full planning permission.

This tool helps you:

Check if your extension, loft conversion, or outbuilding might qualify as permitted development
Understand the key limitations and restrictions that apply to your property type
Identify if any constraints (like conservation areas) affect your permitted development rights
Get clear guidance on next steps based on your specific project

Permitted Development Checker tool interface

Our step-by-step PD checker guides you through the assessment process

Best For

Homeowners in the early planning stages who want to understand if their project might require planning permission before investing in detailed plans.

Use PD Checker Tool

Roof Volume Calculator

Calculate the volume addition of your proposed loft conversion to check if it falls within the permitted development allowances (40m³ for terraced houses, 50m³ for semi-detached and detached houses).

This tool helps you:

Calculate the volume of different types of roof alterations (dormers, hip-to-gable, etc.)
Determine if your loft conversion plans are within permitted development limits
Understand how different design choices affect the overall volume
Get a printable report for your records or discussions with builders

Calculate dormer, hip-to-gable, and other loft conversion volumes

Best For

Homeowners planning loft conversions who need to ensure their designs stay within permitted development volume allowances.

Use Roof Volume Calculator

Extension Depth Calculator

Determine the maximum depth your rear extension can extend under permitted development rights, taking into account your property type and whether you're using the standard allowance or the larger homes scheme.

This tool helps you:

Calculate maximum extension depth based on your house type (detached, semi-detached, terraced)
Understand different allowances under standard PD rights vs. the larger homes scheme
Visualize the potential extension footprint
Check if your plans fall within the 50% garden coverage rule

Calculate maximum permitted extension depths for your property type

Best For

Homeowners planning rear extensions who want to maximize the space they can add without requiring planning permission.

Use Extension Depth Calculator

GIA/GEA Calculator

Calculate and compare Gross Internal Area (GIA) and Gross External Area (GEA) for your property, which is useful for planning applications, valuations, and understanding the impact of wall thickness on usable space.

This tool helps you:

Calculate both GIA (internal measurements) and GEA (external measurements)
Understand the difference between various floor area measurements
Generate area calculations for planning applications
Compare existing and proposed floor areas

Calculate important floor area measurements for planning and valuation

Best For

Property developers, homeowners applying for planning permission, and anyone needing precise floor area measurements for valuations or planning purposes.

Use GIA/GEA Calculator

Planning Constraints Checker

Identify planning constraints that might affect your property, such as conservation areas, green belt, flood zones, or tree preservation orders, which could impact your development potential.

This tool helps you:

Check for key planning constraints affecting your property
Understand how specific constraints might limit development options
Identify additional consents or surveys you might need
Get guidance on how to address constraints in your planning application

Identify constraints that could affect your development potential

Best For

Anyone researching a property's development potential, either for purchase decisions or before planning a project.

Use Constraints Checker

45-Degree Rule Calculator

Check if your extension might impact neighbours' light by applying the 45-degree rule, a planning guideline used by many local authorities to assess potential overshadowing.

This tool helps you:

Apply the 45-degree rule to your extension plans
Visualize potential light impact on neighbouring properties
Adjust your extension depth or position to minimise impact
Generate diagrams for pre-application discussions or planning submissions

Assess potential light impact on neighbouring properties

Best For

Homeowners planning extensions who want to ensure their proposals won't cause unacceptable overshadowing to neighbouring properties.

Use 45-Degree Rule Calculator

How to Get the Most from Our Tools

Tips for Using Our Planning Tools

Have your measurements ready: For most tools, you'll need accurate measurements of your property and proposed changes
Check your property type: Different rules apply to detached, semi-detached, and terraced houses
Know your constraints: Use the Constraints Checker first to identify any special designations affecting your property
Save or print results: Keep copies of tool outputs for discussions with architects, builders, or planning officers
Combine tools: Use multiple tools together for a comprehensive understanding of your project's planning position

Important Disclaimer

While our tools provide guidance based on current regulations, they cannot account for every local variation or specific circumstance. The results should be treated as indicative rather than definitive.

For complete certainty, consider applying for a Lawful Development Certificate from your local authority or seeking professional planning advice.

Updates and Accuracy

Our tools are regularly updated to reflect changes in planning regulations. All calculations are based on current planning rules as of April 2025. If you notice any discrepancies or have suggestions for improvement, please contact us.

Planning a Project?

Our tools work best alongside our detailed planning guides:

Need Professional Help?

For complex projects, consider engaging a planning professional:

Expert Tip

Always check with your local authority about any local planning policies or Article 4 Directions that might affect your permitted development rights. These local variations aren't always captured by general tools.

What Our Users Say

"The PD Checker saved me so much time and worry. I was able to confirm my extension plans fell under permitted development before spending money on an architect."

- Sarah Johnson, Homeowner in Bristol

"As an architect, I regularly recommend the Roof Volume Calculator to clients planning loft conversions. It helps them understand the limitations before we get too far into the design process."

- David Chen, Architect

"The Constraints Checker alerted me to a conservation area designation I wasn't aware of when buying my property. This was invaluable information before planning our renovation."

- Mark and Jessica Taylor, London

"The 45-Degree Rule Calculator helped me adjust my extension plans to avoid problems with my neighbour. We ended up with a design that worked for everyone."

- Emma Wilson, Homeowner in Manchester

Common Questions About Our Tools

How accurate are the planning tools?

Our planning tools are designed to provide guidance based on current national planning regulations in England. They aim to be as accurate as possible, but cannot account for every local variation or specific circumstance.

The tools are most accurate when:

You provide precise measurements and information
Your property doesn't have unusual features or constraints
Your local authority follows standard national guidelines without significant local variations

For complete certainty, particularly for borderline cases or significant investments, we recommend seeking professional advice or applying for a Lawful Development Certificate from your local authority.

Do I need to use multiple tools for my project?

Yes, for most projects, using multiple tools will give you the most comprehensive understanding of your planning position. We recommend a typical workflow like this:

Start with the Constraints Checker to identify any special designations affecting your property
Use the PD Checker to determine if your project might qualify as permitted development
Use specialized calculators (e.g., Roof Volume Calculator for loft conversions or Extension Depth Calculator for extensions) to verify specific aspects of your proposal
Check impact assessments like the 45-Degree Rule Calculator to evaluate potential effects on neighbours

This multi-tool approach provides a more robust assessment than relying on any single tool and helps identify potential issues from different angles.

Can I rely on tool results for my planning application?

Our tools provide useful guidance, but planning decisions ultimately rest with local authorities. The results from our tools can be used to:

Inform initial project feasibility before investing in detailed plans
Guide discussions with architects, builders, or planning consultants
Help prepare supporting statements for planning applications
Identify potential issues that may need to be addressed in your application

However, tool results should not be considered definitive or legally binding. For formal confirmation, apply for a Lawful Development Certificate or full planning permission from your local authority.

We recommend including tool outputs as supporting evidence in your application, but they should complement rather than replace professional drawings, statements, and other required documentation.

Do your tools account for my local authority's specific policies?

Our tools are based on national planning regulations for England rather than local variations. They do not account for:

Article 4 Directions that remove specific permitted development rights in certain areas
Local Plan policies that might be more restrictive than national guidelines
Supplementary Planning Documents (SPDs) with specific design guidance
Neighbourhood Plans with additional local restrictions
Special local designations not captured in national datasets

While our Constraints Checker identifies major designations like conservation areas and listed buildings, we recommend checking your local authority's planning portal for specific local policies that might affect your project.

Are these tools relevant to Scotland, Wales, and Northern Ireland?

Our tools are primarily designed for properties in England, as planning regulations differ across the UK nations:

Scotland has its own planning system with different permitted development rights and regulations
Wales has similar but not identical permitted development rights to England
Northern Ireland has its own planning regulations with different criteria

While some general principles apply across all UK nations, the specific measurements, allowances, and criteria built into our tools are based on England's planning regulations. If your property is in Scotland, Wales, or Northern Ireland, consider the tool results as approximate guidance only, and consult your local planning authority for nation-specific regulations.

View All FAQs

Ready to plan your project?

Use our interactive tools to check if you need planning permission and understand the regulations that apply to your property.

Start with the PD Checker Learn About Permitted Development