Deck, Fence & Outdoor Calculators
Measure once, then let Deck, Fence & Outdoor Calculators build the material list. Count deck boards, balusters, pickets, and posts. Size footings, coops, and round pens. Price sheds, carports, and seawalls, or plan sod and grass seed.
Using Deck, Fence & Outdoor Calculators
Backyard projects look simple on paper. The trouble starts at the lumber yard, when the count comes up short or the posts are too long. Deck, Fence & Outdoor Calculators turn yard measurements into a buy list.
Most of these tools use one of three kinds of math. Some count evenly spaced parts, like boards and pickets. Some check a code rule, like guard spacing or post depth. Others turn size into cost.
Deck Tools
The Decking Calculator counts boards, screws, and joists for the deck surface. The Deck Footing Calculator sizes footings and concrete. The Deck Post Spacing Calculator finds how many posts a beam needs and how far apart they sit.
For the railing, the Baluster Calculator and Spindle Spacing Calculator find the count and the gap. The Deck Slope Calculator sets a slight pitch so water runs off. The Deck Stain Calculator estimates gallons from area and coats. The Balcony Size Calculator works out area and dimensions for a balcony.
Counting Deck Boards
Board count depends on board width plus the gap between boards. A 5-1/2 in board with a 1/8 in gap covers 5-5/8 in per row.
A deck 12 ft deep is 144 in. Divide 144 by 5.625 and you get 25.6. Round up to 26 rows. Then multiply rows by boards per row, based on deck length and board length.
Check the gap your decking maker lists. Wood and composite boards often call for different spacing.
Deck Guard Rules
The IRC calls a railing a guard. Section R312 sets when you need one and how it must be built.
| Rule | IRC requirement |
|---|---|
| When a guard is required | Walking surface more than 30 in above grade, within 36 in of the edge |
| Minimum guard height | 36 in |
| Openings in the guard | A 4 in sphere must not pass |
| Guards along stairs | At least 34 in, measured from the nosings |
| Triangle at stair riser and tread | A 6 in sphere must not pass |
The 4 in rule applies everywhere in the guard. That includes the gap between the deck and the bottom rail. Some states and cities raise the guard height to 42 in, so check local code.
Spacing Balusters Evenly
To keep gaps under 4 in, pick a target gap a little smaller. Then work out the count.
$$\text{Balusters} = \frac{\text{Opening} + \text{Gap}}{\text{Baluster width} + \text{Gap}}$$
Round the result up to a whole number. Then find the real gap by dividing the leftover space evenly.
Take a 96 in opening with 1.5 in balusters and a 3.5 in target gap. The formula gives 19.9, so use 20 balusters. That leaves 66 in of open space across 21 gaps. Each gap is about 3.14 in, which passes the 4 in test.
Fence Tools
The Fence Calculator gives posts, rails, and panels for a fence line. The Wood Fence Calculator adds pickets, concrete, and cost. The Vinyl Fence Cost Calculator prices panels and posts for vinyl.
The Fence Picket Calculator counts pickets from length, width, and spacing. The Rectangle Fence Perimeter Calculator finds total fence length around a rectangle, which is two times length plus width. The Barbed Wire Fence Calculator estimates rolls, posts, and staples for field fencing.
Posts and Pickets
A straight run needs one more post than it has sections. A 100 ft run with posts every 8 ft has 12.5 sections. Round up to 13 sections, which means 14 posts. Add extra posts for corners and gates.
For a privacy fence with no gap, 5-1/2 in pickets need about 2.2 per foot. That is about 219 pickets for 100 ft before waste.
How Deep to Set Posts
The Fence Post Depth Calculator applies two common rules. Use whichever gives the deeper hole.
The first is the one-third rule. Bury about one-third of the total post length. An 8 ft post for a 6 ft fence goes about 32 in deep.
The second is frost depth. In cold areas, the bottom of the footing should sit below the local frost line. Many installers add about 6 in below it. Frost depth ranges from a few inches in the Gulf states to several feet in the northern states.
Gate and corner posts carry more load. Set them deeper than line posts. Your local building department can confirm frost depth and any fence rules.
Animal and Garden Structures
The Chicken Coop Size Calculator sizes a coop and run for your flock. A common guideline is 3–4 sq ft per standard bird inside the coop. Many keepers plan about 8–10 sq ft per bird in the run. Local ordinances may set their own minimums.
The Round Pen Calculator finds pen size and panel count. Circumference is pi times diameter. A 60 ft pen is about 188.5 ft around. With 12 ft panels, that is about 16 panels.
The Hoop House Calculator works out hoop spacing, covering, and overall size for a growing tunnel.
Cost Tools
Four tools help you price a project before calling contractors. The DIY Shed Cost Calculator totals materials for a shed. The Carport Cost Calculator and Lean To Cost Calculator do the same for open shelters. The Seawall Cost Calculator estimates a seawall by length and type.
Prices vary a lot by region and season. Enter your local material and labor rates for the closest estimate.
Lawn Tools
The Sod Calculator finds rolls or pallets for a lawn. Pallet coverage varies by sod farm, so check the supplier’s figure.
The Grass Seed Calculator uses seeding rates per 1,000 sq ft. Rates depend on seed size.
| Grass type | Typical new lawn rate per 1,000 sq ft |
|---|---|
| Tall fescue | About 6–10 lb |
| Perennial ryegrass | About 7–8 lb |
| Kentucky bluegrass | About 2–3 lb |
| Bermuda (hulled) | About 1–2 lb |
Overseeding a thin lawn usually takes about half the new lawn rate. A 3,500 sq ft new lawn at 6 lb of tall fescue needs about 21 lb. The seed bag lists the rate for that product.
Common Mistakes
Forgetting the end post. Sections and posts are not the same count. A straight run always needs one extra post.
Measuring baluster gaps center to center. The 4 in rule applies to the clear opening between parts.
Setting posts by habit. A depth that works in a warm state can heave in a cold one.
Buying stain for one coat. Rough or thirsty wood soaks up more. Check the can’s coverage and plan for the coats it calls for.
FAQs
How far apart can deck balusters be?
Close enough that a 4 inch sphere cannot pass between them. Most builders aim for a gap of about 3 to 3-1/2 inches.
When does a deck need a railing?
Under the IRC, when the walking surface is more than 30 inches above grade within 36 inches of the edge. The guard must be at least 36 inches tall.
How deep should a 6 ft fence post be?
An 8 ft post is usually set about 32 inches deep under the one-third rule. In cold climates, go below the frost line if that is deeper.
How many fence posts do I need?
Divide the run length by post spacing and round up for sections. Add one post for a straight run, plus extra for corners and gates.
How much grass seed per 1,000 square feet?
It depends on the grass. Tall fescue often takes about 6–10 lb, while Kentucky bluegrass takes about 2–3 lb. Overseeding uses about half.
How much space do backyard chickens need?
A common guideline is 3–4 sq ft per bird inside and about 8–10 sq ft per bird in the run. Larger breeds need more.