Above-Ground Deck Load Capacity Calculator
Get a rough estimate of how much weight your deck can safely support based on joist dimensions, spacing, and span length. This is an educational estimate only — always consult a structural engineer for final decisions.
About this calculator
Estimate the safe live load capacity of a residential deck based on joist spacing, span, and lumber size to help plan furniture and gatherings.
Frequently Asked Questions
Is this a substitute for a structural engineer's assessment?
No. This calculator gives a rough educational estimate only. Always have a licensed professional inspect your deck before adding heavy loads like hot tubs.
Why does joist spacing matter?
Closer joist spacing (like 12 inches vs 24 inches) distributes weight across more support members, increasing overall load capacity.
What counts as 'live load'?
Live load includes people, furniture, and movable items — as opposed to 'dead load' which is the weight of the deck structure itself.