Yard Grading & Drainage Planner
Standing water against the house, a soggy low spot, or a yard that just won't drain? Describe the problem and the area, and this planner returns everything the three separate calculators won't tell you together — the slope you need away from the foundation, the fill dirt to order (with compaction), and a sized French drain with gravel, pipe, and a realistic cost range.
Estimate only — not professional advice. Always verify results independently before purchasing materials or beginning work. Terms of Use
What is Yard Grading & Drainage Planner?
The Yard Grading & Drainage Planner is an end-to-end tool for fixing surface water around a home. Most online calculators solve one slice of the problem — a slope calculator, a fill-dirt calculator, a French drain calculator — and leave you to stitch the numbers together. This planner composes them into a single plan: it sets the correct slope, sizes the soil you need to build that slope, and (optionally) designs the drain that carries water the rest of the way to a safe outlet. Grading is the act of shaping the ground so water flows away from the structure instead of toward it. The single most important rule comes from the International Residential Code (IRC R401.3): the ground must fall a minimum of 6 inches within the first 10 feet measured away from the foundation — a 5 percent slope. When you choose "Water pools near the foundation," the planner enforces that 5 percent minimum automatically, even if you pick a gentler target, because anything less is the leading cause of wet basements and foundation damage. Beyond the first 10 feet, a gentler 2 percent slope (a quarter inch per foot) is enough to keep surface water moving across a lawn. The fill volume is modeled as a tapering wedge: the new grade is highest against the house and feathers down to meet the existing ground at the far edge of the run. Because the added soil starts at full depth and tapers to nothing, the average depth is half the required fall — so the neat (in-place) volume equals the graded area multiplied by half the fall. That neat volume is then increased by a swell-and-compaction factor, because the loose dirt you order from the yard compacts down once it's placed and tamped. Fill dirt swells about 25 percent, screened topsoil about 20 percent, and sandy soil about 15 percent. The result is the volume to actually order, in cubic yards and tons, so a single delivery covers the job. The optional French drain handles the water that grading alone can't shed — a persistent low spot, a spring line, or a flat area with nowhere to slope. The planner sizes a standard 12-inch-deep, 6-inch-wide gravel trench running the width of the wet edge, with a 4-inch perforated pipe and the washed gravel needed to surround it. Pair the two and you have a complete water-management plan: grade the surface to move the easy water, and drain the stubborn water that's left. The cost range combines typical installed pricing — roughly $1 to $2 per square foot for grading work and $10 to $50 per linear foot for a French drain — so you can sanity-check a contractor quote or decide whether the job is a weekend of rented-machine DIY or a call to a pro. It is an estimate, not a bid: rock, tree roots, restricted access, and haul-off of excess spoil all move the real number.
How to Calculate
- Choose what you are fixing — foundation pooling, a yard low spot, or a general regrade
- Enter the width of the problem area measured along the house (or along the wet edge)
- Enter how far out from the house you want to establish the slope (the run)
- Pick a target slope — foundation jobs are automatically held to the 5% code minimum
- Select your fill material so the planner applies the right compaction and weight
- Choose whether to add a French drain for water that grading alone won't clear
- Order the fill soil in cubic yards (or tons), plus the drain gravel and 4-inch pipe if included
- Use the cost range to budget the project or check a contractor's quote
Formula
Effective slope (%) = max(your target, 5% if fixing the foundation per IRC R401.3) Required fall (in) = (Slope / 100) x Run (ft) x 12 Graded area (sq ft) = Width x Run Neat fill (cu yd) = Area x (Fall in ft / 2) / 27 [tapering wedge, average depth = fall / 2] Fill to order (cu yd) = Neat fill x Swell factor (1.25 dirt, 1.20 topsoil, 1.15 sand) Soil weight (tons) = Fill to order x Density (1.1 dirt/topsoil, 1.3 sand) French drain length (ft) = Width of the wet edge Drain gravel (cu yd) = Length x 0.5 sq ft x 0.85 / 27 [0.5 sq ft trench, 15% displaced by pipe] Cost range = Area x ($1 to $2) + Drain length x ($10 to $50)
Example Calculation
Water pooling against a 20 ft stretch of foundation, grading out 10 ft, fill dirt, with a French drain: Effective slope = max(2%, 5%) = 5% (foundation minimum enforced) Required fall = (5 / 100) x 10 x 12 = 6 inches in the first 10 ft (meets code) Graded area = 20 x 10 = 200 sq ft Neat fill = 200 x (0.5 ft / 2) / 27 = 1.85 cu yd Fill to order = 1.85 x 1.25 = 2.31 cu yd (about 2.5 tons) French drain length = 20 ft Drain gravel = 20 x 0.5 x 0.85 / 27 = 0.31 cu yd, with 20 ft of 4 in perforated pipe Cost range = 200 x ($1–$2) + 20 x ($10–$50) = $400 – $1,400
Frequently Asked Questions
How much slope do I need away from my foundation?
The International Residential Code (R401.3) requires the ground to drop at least 6 inches within the first 10 feet away from the foundation — a 5 percent slope. This planner enforces that 5 percent minimum automatically when you select the foundation problem, even if you choose a gentler target. Beyond the first 10 feet, a 2 percent slope (a quarter inch per foot) is enough to keep surface water moving away from the house.
How much fill dirt do I need to regrade my yard?
It depends on the area and how much fall you are building. Because a regrade is a wedge — deepest at the house, tapering to nothing at the far edge — the average depth is half the required fall. The planner multiplies the graded area by half the fall to get the in-place volume, then adds 15 to 25 percent for compaction depending on the material, because loose dirt settles once it is placed and tamped. Order the larger 'fill to order' figure so a single delivery finishes the job.
Do I need a French drain or just better grading?
Grading is always the first fix — if the surface slopes away from the house, most water never becomes a problem. Add a French drain when grading alone can't shed the water: a persistent low spot, a high water table or spring line, or a flat area with nowhere to slope. The two work together — grade the surface to move the easy water and drain the stubborn water that's left. The planner can size both at once.
What size pipe does a French drain use?
A 4-inch perforated pipe handles almost all residential French drains. Use rigid perforated PVC or corrugated HDPE wrapped in a filter sock, and surround it with clean washed gravel. Step up to 6 inches only for very large catchment areas or long runs collecting heavy flow. The drain must always slope at least 1 percent toward a daylight outlet, ditch, dry well, or storm connection — a dead-end drain eventually fills and stops working.
How much does it cost to regrade a yard and add drainage?
Grading work typically runs $1 to $2 per square foot, and a professionally installed French drain runs about $10 to $50 per linear foot depending on depth, access, and outlet distance. The planner combines both into a range. Treat it as a budgeting estimate, not a bid — buried rock, tree roots, tight access, and hauling away excess soil can all push the real cost higher. Get quotes for the actual job.
Can I regrade the yard myself?
Small regrades — a single low spot or 10 to 20 feet of foundation edge — are realistic DIY with a wheelbarrow, a rake, a hand tamper, and a string line or laser level to hold the slope. Larger jobs, anything needing a skid-steer, or work near utilities, retaining walls, or property lines are usually better hired out. Whatever the approach, verify the 6-inch-in-10-feet fall at the foundation with an actual level — eyeballing slope is unreliable past a few feet.