Decking Calculator & Board Quantity Estimator
Use our decking calculator to estimate how many decking boards you need, calculate approximate linear metres, allow for waste and choose the right anti-slip or non-slip decking product for your project.
How to Calculate Decking Boards
To estimate decking quantities manually, multiply the deck length by the deck width to calculate the total area in square metres. Then divide the area by the decking board width to estimate the linear metres required. Finally, add a waste allowance and divide by your chosen board length to estimate the number of boards.
Free Decking Calculator
Enter the length and width of your decking area below to estimate the square metre area, linear metres of decking required and the approximate number of decking boards needed. This decking board calculator is designed as a useful guide for garden decking, commercial walkways, boardwalks, bridges, platforms and public access routes.
Calculate Your Decking Boards
Enter your deck size and select the board width and board length you are considering. This calculator provides an estimate only and should always be checked before ordering.
Common Decking Board Widths
Different decking products use different board widths, so it is important to select the closest width in the calculator before estimating quantities. GripDeck® can help confirm the correct board size before you order.
| Board Width | Typical Product Type | Useful For |
|---|---|---|
| 115mm | Selected timber or ThermoDeck® profiles | Projects using narrower decking boards. |
| 138mm | Composite decking boards | SmartBoard® composite decking calculations. |
| 145mm | Common softwood and hardwood decking size | Most standard GripDeck® anti-slip timber decking estimates. |
| 195mm | Wider specialist timber boards | Bridges, walkways and project-specific board sizes. |
What to Do After Using the Decking Calculator
Your decking calculation is a useful starting point, but final quantities can change depending on board direction, board spacing, substructure layout, cutting waste, steps, edging details and the decking product selected.
1. Choose Your Decking Type
Decide whether softwood anti-slip decking, hardwood decking, ThermoDeck®, composite decking or retrofit anti-slip inserts are best for your project.
2. Confirm Board Size
Board width, thickness and length all affect the quantity required and the final price.
3. Request a Quote
Send us your measurements, preferred product and delivery postcode for an accurate quotation.
Need a Decking Quote?
Use your calculator result as a starting point and send it to GripDeck® for a project-specific quotation.
Request a Quote Request SamplesWhich Decking Product Should I Calculate For?
The calculator can be used for different decking products, but the board width, board length and waste allowance should match the material you intend to order.
| Project Type | Recommended Product | Calculator Tip |
|---|---|---|
| Garden decking, schools and general walkways | Softwood anti-slip decking | 145mm is commonly used for many softwood GripDeck® boards. |
| Premium commercial or public access projects | Hardwood anti-slip decking | Check the chosen species and board profile before calculating. |
| Modern timber decking with improved stability | ThermoDeck® | Use the correct ThermoDeck® board width before ordering. |
| Low-maintenance garden decking | Composite decking | Use the composite board width and allow for trims and fixings separately. |
| Existing grooved decking | RetroGrip® inserts | This calculator estimates boards, not insert quantities. Contact us for retrofit advice. |
Choose the Right Decking Product
Softwood Anti-Slip Decking
Cost-effective European Redwood anti-slip and non-slip decking for gardens, schools, walkways and commercial projects.
View Product
Hardwood Anti-Slip Decking
Premium hardwood decking with factory-applied anti-slip inserts for long-term performance on commercial and high-end projects.
View Product
ThermoDeck®
Thermally modified timber decking with anti-slip inserts for a stable, attractive and lower-maintenance timber finish.
View ProductTypical Decking Project Sizes
Use the examples below as a quick guide when planning decking board quantities. Every project is different, so always check your final measurements before ordering.
| Deck Type | Example Size | Approx. Area | Typical Use |
|---|---|---|---|
| Small Garden Deck | 3m x 3m | 9m² | Small seating area or patio deck |
| Medium Garden Deck | 4m x 5m | 20m² | Family seating area or outdoor dining space |
| Large Garden Deck | 6m x 5m | 30m² | Larger entertaining area or hot tub surround |
| Commercial Walkway | 10m x 2m | 20m² | Access route, boardwalk or public walkway |
Decking Calculator Notes & Quantity Advice
Allow for Waste
Most decking projects should allow at least 5–10% waste. Angled, diagonal, stepped or complex layouts may require more.
Check Board Direction
The direction decking boards are laid can affect both the number of boards required and the cutting waste.
Consider Anti-Slip Inserts
For around 90% of anti-slip decking applications, 2 inserts are suitable. Where the main travel direction runs along the board, 3 inserts may be preferred.
Useful Resources
Slippery Decking Guide
Learn why decking becomes slippery and how to choose the right anti-slip solution.
Read GuideAnti-Slip Test Results
View wet and dry slip resistance results for GripDeck® decking products.
View ResultsDecking Supply
Learn how GripDeck® supplies anti-slip decking to trade, commercial and domestic customers.
View Supply InfoSee GripDeck® Decking in Use
These case studies show how GripDeck® anti-slip decking has been used on real visitor attractions, heritage, pier and public access projects.
Shotley Pier
Reclaimed Greenheart decking with GripDeck® inserts supplied for pier restoration.
View Case Study
Turn Your Decking Calculation Into a Quote
Send your measurements, calculator result, drawings or photos to GripDeck® and we will help confirm the correct quantity, product type, board size and specification.
Request a Quote Contact GripDeck®Frequently Asked Questions
How do I calculate how much decking I need?
Measure the length and width of the decking area in metres, multiply them to calculate the square metre area, then divide by the board width to estimate linear metres of decking required.
How many decking boards do I need?
The number of boards depends on the total area, board width, board length, waste allowance and board direction. Use the calculator above as a guide.
How much waste should I allow for decking?
For simple square or rectangular decks, allow around 5–10% waste. For angled, complex or irregular layouts, allow around 10–15% or more.
What decking board width should I choose?
145mm is a common decking board width for timber decking, but GripDeck® can supply other widths depending on the product, timber species and project specification.
Can GripDeck® check my decking calculation?
Yes. Send us your measurements, sketch or drawing and our team can help check quantities before you order.
Does the calculator include gaps between decking boards?
The calculator provides a general estimate based on board width. Actual quantities can vary depending on board spacing, fixing layout, trimming, edging and installation details.
Can I use this calculator for composite decking?
Yes, but select the closest composite decking board width and remember that trims, clips, fixings and accessories should be calculated separately.
Does the calculator include joists and substructure?
No. This calculator estimates decking boards only. Joists, posts, fixings, edging, fascia boards and substructure materials need to be calculated separately.