A fence calculator turns a fence line into a material list. Enter the total length, the number of corners and gates, the height and the post spacing, and Contruva’s free fence calculator tells you how many posts, rails and pickets to buy, how many gate kits, how many bags of concrete to set the posts, and roughly how many screws, plus the material cost at your prices.
Open the free fence calculator in your browser. No login, no email, nothing to pay.
Open the free toolIt’s built for wood privacy and picket fences, works in feet or metres, and needs no login. Below is the math behind each line so you can check it, a worked example, and the site questions a calculator can’t answer for you: frost depth and what’s buried under the yard.
How to use the fence calculator
Total length including gate openings, number of corners, number of gates and their width, and post spacing (6 or 8 ft, or 1.8 or 2.4 m).
4, 6 or 8 ft. The tool suggests 2 rails per section for a 4 ft fence and 3 for 6 and 8 ft; change it if your design differs.
Actual picket width (5.5 in for a 1×6, 3.5 in for a 1×4), the gap between pickets (0 for a tight privacy fence) and a waste percentage.
Post size (4×4 or 6×6), hole depth and diameter, and the concrete bag you’ll use: 80, 60, 50 or 40 lb, or 30 kg.
Your supplier’s price per post, rail, picket, gate kit, bag and per 100 screws. The cost breakdown fills in as you type.
Walk the line with a wheel or tape and write down each straight run, every corner and where the gates go. A rough “about 150 feet” is how fences come up three posts short.
How many fence posts do I need?
Start with the fence that isn’t gate: total length minus the gate openings. Divide that by the post spacing and round up to get sections. Each section needs a post at one end, the line needs one more to start it, and then the calculator adds:
- One post per corner. A run rarely divides evenly by the post spacing, so each corner usually leaves one short section and one extra post.
- One post per gate. A gate opening needs a post on both sides, and the second one isn’t shared with a fence section.
| Line | Formula |
|---|---|
| Fence length | Total length − (gates × gate width) |
| Sections | (Fence length ÷ post spacing, rounded up) + corners |
| Posts | (Fence length ÷ post spacing, rounded up) + 1 + corners + gates |
| Post length | Fence height + hole depth, rounded up to the next even foot (8 ft minimum) |
A straight 48 ft run with no gates at 8 ft spacing is 6 sections and 7 posts. Add corners and gates and the count climbs, which is why measuring each run matters. If your runs happen to divide evenly, you’ll have a spare post or two, which is cheaper than a second trip.
How many rails and pickets do I need?
Rails are counted per section. At 8 ft spacing, each rail is one 8 ft 2×4. At 6 ft spacing, the calculator assumes 12 ft 2×4s that span two sections, which is how most crews frame a 6 ft bay and saves cutting.
| Fence height | Usual rails per section | Why |
|---|---|---|
| 4 ft | 2 | Short pickets don’t need a middle rail |
| 6 ft | 3 | A middle rail stops pickets from bowing |
| 8 ft | 3 | Taller pickets need the support; some designs use 4 |
Pickets cover the whole run, gates included, because gate frames get the same pickets as the fence. The count is total length in inches ÷ (picket width + gap), plus waste. Use the actual width: a 1×6 picket is 5.5 in, not 6. For a picket fence with spaces, a gap close to the picket width is common; set it to whatever your design or HOA calls for.
Fasteners are two screws or nails per picket at every rail, plus two at each end of each rail, plus 5% spare. Rail brackets, if you use them, aren’t counted.
How much concrete per fence post?
Each hole is a cylinder with a square post in the middle. The calculator works out the cylinder, subtracts the post, and divides by the yield of your bag.
| Step | Formula |
|---|---|
| Hole volume | π × (diameter ÷ 2)² × depth |
| Minus the post | Post width² × depth (3.5 in for a 4×4, 5.5 in for a 6×6) |
| Cubic feet | Cubic inches ÷ 1,728 |
| Bags | Total cubic feet for all posts ÷ yield per bag, rounded up |
| Bag | Approximate yield | Bags per 10 in × 48 in hole (4×4 post) |
|---|---|---|
| 80 lb | 0.60 cu ft | 3.1 |
| 60 lb | 0.45 cu ft | 4.1 |
| 50 lb | 0.375 cu ft | 4.9 |
| 40 lb | 0.30 cu ft | 6.1 |
| 30 kg | about 0.014 m³ (0.49 cu ft) | 3.7 |
The 40, 50 and 60 lb yields are from Quikrete’s Concrete Mix data sheet and the 80 lb yield from Quikrete’s product information (checked November 2026). Canadian 30 kg bags vary by brand, so read the yield on the bag you’re buying. Fast-setting post mixes often have their own yield and setting instructions; follow the bag.
Worked example: 150 ft of 6 ft privacy fence
A backyard fence 150 ft long with two corners and one 4 ft gate. 6 ft high, posts every 8 ft, 3 rails per section, 1×6 pickets (5.5 in) installed tight with 5% waste. 4×4 posts in holes 10 in across and 48 in deep, 80 lb bags. Sample prices: $20 a post, $8 a rail, $4 a picket, $45 a gate kit, $9 a bag and $10 per 100 screws. These are placeholders to show the math, not market prices.
150 − 4 ft gate.
146 ÷ 8 = 18.25, rounded up to 19, + 2 corners.
19 + 1 + 2 corners + 1 gate. Height 6 ft + 4 ft in the ground = 10 ft posts.
21 sections × 3 rails.
1,800 in ÷ 5.5 = 327.3, + 5% = 343.6, rounded up.
Each hole takes 1.84 cu ft (3.07 bags). 23 holes = 42.35 cu ft ÷ 0.6 = 70.6.
344 pickets × 3 rails × 2 + 63 rails × 4 = 2,316, + 5%.
| Line | Quantity | Cost |
|---|---|---|
| Posts | 23 | $460.00 |
| Rails | 63 | $504.00 |
| Pickets | 344 | $1,376.00 |
| Gate kit | 1 | $45.00 |
| Concrete | 71 bags | $639.00 |
| Screws | 2,432 | $243.20 |
| Material total | $3,267.20 |
Switch the same fence to 6 ft spacing and you get 27 sections and 41 twelve-foot rails. Switch to 30 kg bags and the concrete becomes 86 bags. Three bags of 80 lb per hole is a lot of mixing on 23 posts, so it’s worth pricing a short load of ready-mix or a mixer rental against the bags.
Post depth, frost and locates
The calculator sets concrete to whatever depth you enter. Picking that depth is a site decision.
- Frost. In much of Canada, frost reaches 4 ft (1.2 m) or deeper, and posts set shallower can heave. Several Ontario municipal deck guides use 1.2 m as the minimum footing depth for attached decks (checked November 2026). Fences aren’t decks, but it’s a useful benchmark; ask your municipality what they expect.
- Hole size. About three times the post width is a common rule of thumb: 10 to 12 in for a 4×4. A bell-shaped bottom resists heave better than a straight cylinder.
- Drainage. A few inches of gravel at the bottom helps water drain away from the post end. The calculator fills the full depth with concrete, so subtract the gravel depth if you use it.
- Bylaws. Many municipalities limit fence height and set rules for pool enclosures and corner lots. Check before you quote an 8 ft fence.
In Ontario, contacting Ontario One Call for a locate before you dig is required by law and free. Other provinces have their own one-call centres, listed at clickbeforeyoudig.com. In the US, call 811. Book it early; locates take days, not hours.
Fence takeoff mistakes
| Mistake | What happens | The fix |
|---|---|---|
| Counting posts as length ÷ spacing | You’re short the first post, the corners and the gates | Add 1, plus corners and gates |
| Using 6 in for a 1×6 picket | About 8% fewer pickets than you need | Enter the actual width |
| Forgetting pickets on the gate | The gate is bare on install day | Count pickets over the full length |
| Posts too short for the hole depth | Fence ends up lower than quoted | Post length = height + depth |
| Estimating concrete by “a bag a hole” | Two or three bags short per post | Work out the hole volume |
| No locate booked | Delays, or a hit gas or hydro line | Book the locate when the quote is signed |
From material list to a fence quote
Once the list is right, the quote is material plus delivery and disposal, your crew’s hours, auger or skid steer rental if you need one, and your markup. The markup calculator turns that cost into a price. If the customer wants a deck or a gravel strip along the fence line too, the deck calculator and the construction material calculator cover those.
Contruva is built for fence and deck contractors. Your posts, rails, pickets and labour rates live in a price catalog, so a fence quote goes out from the customer’s driveway, they sign it on their phone and pay the deposit through online payments, and job costing shows whether the fence made the margin you priced. It’s all in Contruva Pro at $249.99 CAD a month. Try it free for 7 days, no credit card needed.