{"id":"fence-post-calculator","name":"Fence Post Spacing Calculator","shortName":"Post Spacing","canonicalUrl":"https://calcurhome.com/calculators/fence-post-calculator","catalogUrl":"https://calcurhome.com/api/calculators","category":{"id":"decks-fences","name":"Decks & fences","url":"https://calcurhome.com/calculators/category/decks-fences"},"language":"en-US","audience":"US homeowners, DIYers and home-project planners","primaryKeyword":"fence post spacing calculator","secondaryKeywords":["fence post calculator","fence post count calculator","fence section spacing calculator","how many fence posts do I need"],"description":"Calculate fence-post count and actual section spacing for equal runs, with a supplemental concrete estimate from entered hole dimensions and yield.","directAnswer":"Divide each equal fence run by maximum spacing and round up to sections; each independent run then needs one more post than sections. The supplemental concrete estimate uses entered hole geometry and bag yield. Use the dedicated post-hole concrete calculator when concrete quantity is the primary task.","inputs":[{"key":"runLength","label":"Length per equal run","unit":"ft","defaultValue":48,"min":0.1,"step":0.1},{"key":"runs","label":"Equal fence runs","unit":"runs","defaultValue":2,"min":1,"step":1},{"key":"postSpacing","label":"Maximum post spacing","unit":"ft","defaultValue":8,"min":0.1,"step":0.1},{"key":"holeDiameter","label":"Hole diameter","unit":"in","defaultValue":12,"min":0.1,"step":0.1},{"key":"holeDepth","label":"Concrete-filled depth","unit":"ft","defaultValue":3,"min":0.1,"step":0.1},{"key":"postWidth","label":"Actual square post width","unit":"in","defaultValue":3.5,"min":0,"step":0.01},{"key":"bagYield","label":"Mixed concrete yield per bag","unit":"cu ft","defaultValue":0.375,"min":0.001,"step":0.001},{"key":"waste","label":"Concrete allowance","unit":"%","defaultValue":10,"min":0,"max":30,"step":1}],"formula":{"title":"Fence post spacing with supplemental concrete","expression":"Posts = (ceiling(run length ÷ spacing) + 1) × runs; concrete = [πr²depth − post width²depth] × posts × allowance","explanation":"Every independent run has two endpoints around its rounded sections. Concrete fills the cylindrical hole volume remaining after the embedded square post displaces material."},"measurementGuide":["Measure each independent straight run from terminal-post center to terminal-post center.","Use the approved maximum spacing and add separate corner, gate, brace, or transition posts to the final plan.","Measure hole diameter and concrete-filled depth, distinguishing gravel bases or unfilled drainage zones.","Use actual post width and the mixed cubic-foot yield printed for the exact bag size and concrete product."],"buyingTips":["Arrange required utility locating and verify property boundaries, easements, setbacks, and permits before excavation.","Have gate, corner, tall, solid, and high-wind fence posts and foundations designed for their larger loads.","Use posts, concrete, coatings, and fasteners suitable for ground contact, soil chemistry, drainage, and exposure.","Brace posts plumb and follow concrete manufacturer requirements for water, mixing, placement, cure, and loading."],"workedExample":{"title":"Two equal 48-foot fence runs","scenario":"Two 48-foot runs use 8-foot spacing, 12-inch holes 3 feet deep, 3.5-inch posts, 0.375-cubic-foot bags, and 10% waste.","result":"Each run has six sections and seven posts; 14 posts need about 32.35 cubic feet of concrete with allowance, or 87 bags."},"commonQuestions":[{"question":"How deep should a fence post hole be?","answer":"Depth depends on fence height and solidity, post and footing design, soil, drainage, frost depth, wind, gates, and local code. A rule of thumb cannot replace local requirements. Gate and corner posts often need larger foundations."},{"question":"Why subtract the post volume from concrete?","answer":"A centered post occupies part of the cylindrical hole, so concrete fills only the remaining space. The subtraction matters for large posts and many holes. Irregular excavation, soil collapse, voids, and overfilling still justify a field allowance."},{"question":"How many concrete bags fill a post hole?","answer":"Calculate the hole’s remaining cubic volume, then divide by the mixed yield printed on the exact concrete bag. Bag weights have different yields. Round up and include allowance for uneven holes, spillage, and grade finishing."},{"question":"Should every fence post use the same footing?","answer":"Not necessarily. Gate, corner, end, brace, tall, and wind-exposed posts can carry much larger loads than intermediate posts. Soil and frost conditions also vary. Use a locally appropriate design rather than applying one hole size everywhere automatically."}],"sources":[{"name":"Call 811","url":"https://call811.com/","note":"Official U.S. one-call resource for arranging underground utility marking before digging."}],"defaultCalculation":{"inputs":{"runLength":48,"runs":2,"postSpacing":8,"holeDiameter":12,"holeDepth":3,"postWidth":3.5,"bagYield":0.375,"waste":10},"result":{"value":"14","unit":"posts","label":"Fence posts required","lines":[{"label":"Sections per equal run","value":"6"},{"label":"Concrete per hole","value":"2.101 cu ft"},{"label":"Concrete with allowance","value":"32.36 cu ft"},{"label":"Concrete bags","value":"87"}],"summary":"The equal runs need 14 posts and approximately 87 concrete bags at the entered mixed yield.","note":"Hole size and depth must follow local frost, wind, soil, fence, gate, drainage, and product requirements. Call the utility-locating service before digging."}},"reviewedOn":"2026-07-23","disclaimer":"Planning estimate only. Verify product coverage, supplier rounding, local codes and structural requirements before purchase or construction."}