Landscaping Calculator
Free landscaping calculator for gardeners and landscapers. Work out garden and lawn areas, turf and topsoil quantities, slopes, gradients and falls, and material pricing. No signup required - works on mobile and desktop.
Garden & Lawn Area Calculator
Calculate plot, lawn, and banked garden areas from dimensions
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Landscaping calculation tips
How much turf do I need?
Measure the lawn area in square metres, then add 5% waste for straight-edged lawns or 10% for curved borders and island beds - curves force more offcuts. Standard turf rolls cover 1 m² each, so a 48 m² lawn with curves needs roughly 53 rolls. Lay within 24 hours of delivery.
Topsoil quantities are volumes, not areas
Multiply the area by the depth you need: 100mm (0.1m) for laying turf, 150mm for new beds, up to 300mm for raised planters. A 50 m² lawn at 100mm needs 5 m³ of topsoil. Bulk bags are typically 0.7-0.9 m³, so check the supplier figure before converting to bags.
Understanding 1-in-X falls
A 1-in-80 fall drops 1 unit vertically for every 80 units of horizontal run - that is 12.5mm per metre. Patios need at least 1-in-80 away from the house; paths are comfortable up to about 1-in-20; anything steeper than 1-in-12 becomes hard work with a wheelbarrow and may need steps.
Sloped banks hold more ground than the plan shows
A banked garden covers more surface than its footprint suggests. On a 30-degree bank, 20 m² of plan is actually 23.1 m² of ground to turf, membrane, or plant. Use the slope factor when ordering materials for banks and terraced gardens or you will run short.
Paving and decking waste allowances
Paving slabs: 10% waste laid straight, 15% for diagonal or circular patterns. Decking boards: 10-15% depending on board length versus deck dimensions. Gravel and decorative aggregate: order by volume at 50mm depth minimum and add 10% for settlement into the sub-base.
Mulch and bark coverage
Mulch is spread at 50-75mm depth to suppress weeds effectively. One cubic metre covers about 13-20 m² depending on depth. Multiply your bed area by depth in metres to get volume, and round up - thin mulch is a false economy because weeds break through within a season.
Formulas used
Lawn / plot area
area = width × length
Slope factor (banks)
factor = 1 / cos(slope°)
Gradient conversions
1 in X = (1/X) × 100% = arctan(1/X)°
Fall over a run
fall = run × tan(gradient°)
Topsoil / mulch volume
volume = area × depth
Material quantity
quantity = (area × (1 + waste%)) / coverage_per_unit
Frequently asked questions
How much turf do I need for my lawn?
Measure the lawn area (width × length in metres), then add 5% waste for straight edges or 10% for curved borders. Standard rolls cover 1 m², so a 40 m² lawn with curves needs about 44 rolls. This calculator works it out and can price it in the Draft Smart Component tab.
How do I calculate topsoil volume?
Multiply the area in square metres by the depth in metres. For turfing, use 100mm (0.1m): a 60 m² lawn needs 6 m³. For new planting beds, use 150mm. Add 5-10% for settlement and uneven ground.
What is a 1-in-80 fall?
A 1-in-80 fall means the surface drops 1 unit for every 80 units of horizontal distance - 12.5mm per metre. It is the standard minimum fall for patios so water drains away from the house. Use the Slope & Gradient tab to convert between 1-in-X, percent, and degrees.
How much gravel do I need for a path?
Multiply the path area by a 50mm depth (0.05m) to get volume in cubic metres, then add 10% for settlement. A 15 m² path needs about 0.83 m³ - roughly one bulk bag. Use a compacted sub-base beneath for a path that lasts.
What is the best free landscaping calculator?
The best free landscaping calculator handles lawn and plot areas, sloped banks, gradients and falls, volumes for topsoil and mulch, and material pricing in one place - exactly what this tool does, free and with no signup. Everything runs in your browser.