Deck joists calculator
Estimate joists from a specified centre spacing.
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Your measurements
Enter your project values. Your estimate updates as you type.
View your estimateExample values are a starting point. Check product yields and specifications before ordering.
YOUR ESTIMATE
Joists to buy
17
Count before waste15
Total material length40.8 m
Whole quantities are rounded up.
How it's calculated
Pieces before waste = round up(run ÷ maximum spacing) + 1 + extras. Apply waste and round up.
Calculations use consistent units for your selected measurements. The waste allowance is applied once to the measured requirement. Whole purchase quantities are rounded up.
What this estimate includes
The spacing must come from an appropriate design. The calculator counts pieces and does not check load capacity.
Quantity and arithmetic estimates only. Use project specifications for installation and design requirements.
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