Deck Load Calculator
Estimate the total load on a deck: enter its size and the live and dead loads to get the design load in psf and total pounds the structure must carry.
How this calculator works
A deck has to carry two kinds of weight: the things placed on it and its own structure. This calculator adds those together into a design load, measured in pounds per square foot (psf), then multiplies by the deck’s area to give the total load the whole structure must support.
The first step sets the design load by adding the live load and the dead load. The second step scales that up to the full deck, so you can see both the intensity per square foot and the overall weight in pounds.
Formula: Design load (psf) = live load + dead load; Total load (lb) = deck area × design load.
Residential decks are typically designed for 40 psf live plus about 10 psf dead.
Worked example
A 12 ft × 16 ft deck (192 sq ft) at 40 + 10 = 50 psf:
- Deck area: 12 × 16 = 192 sq ft
- Design load: 40 + 10 = 50 psf
- Total load: 192 × 50 = 9,600 lb
Notes
It helps to keep the two load types separate in your head. Live load is everything temporary that the deck holds — people standing and moving, furniture, planters, and snow that collects in winter. It varies through the day and the seasons, which is why codes set a minimum to cover a busy, loaded deck.
Dead load is the deck’s own permanent weight: the decking boards, the joists and beams beneath them, the fasteners, and any built-in features. This total load figure is not the end of the process. It feeds directly into sizing the beams and footings, which each carry a portion of it and must be checked against that share.
How to use
Enter your deck’s length and width to set the area, then enter the live and dead loads for your situation. Read off the design load in psf and the total load in pounds. Use the total as the starting demand when you move on to sizing beams, posts, and footings.
This is a planning estimate, not an engineered design. Structural sizing is safety-critical and code-governed — confirm all members, connections, and footings with a licensed structural engineer and your local building code.
Frequently asked questions
What is the difference between live load and dead load?
Live load is the weight that comes and goes: people, furniture, planters, a grill, or snow piled on the surface. Dead load is the fixed weight of the deck itself — the boards, joists, beams, and fasteners that stay in place permanently. The design load adds the two together so the structure is sized for both at once.
Why is 40 psf a common live load for decks?
Many residential building codes call for a minimum deck live load of 40 pounds per square foot, which covers a crowd of people and typical furniture with a margin of safety. It is a widely used starting point, but your local code, snow region, or a hot tub can push the required figure higher, so always confirm the value your project needs.
What does the total load figure tell me?
The total load is the full weight in pounds that the whole deck must carry at its design load. It is a planning number that shows the overall demand on the structure. From there, that load is distributed to beams, posts, and footings, each of which carries a share and must be sized to handle it.
Does a bigger deck always mean a bigger load per square foot?
No. The design load in pounds per square foot stays the same regardless of deck size — it reflects how heavily each square foot is used. A larger deck has a bigger total load simply because it has more square feet, but the per-square-foot demand that drives member sizing does not change with area alone.
Estimates only. Verify quantities with your supplier before purchasing.