Landscape Grade Calculator

Last updated: June 2026

Rise

Run

Derived rise

0.3 m

Grade

Angle

1.72 deg

Ratio

1:33.3

Fall per metre

30 mm

Formula

grade percentage = rise / run x 100. Angle = atan(rise / run) x 180 / pi. Fall per metre in millimetres = grade percentage x 10.

About this calculator

The Landscape Grade Calculator works out slope grade as a percentage, angle, ratio, and fall per metre. It is aimed at practical garden, drainage, ramp, path, driveway, and landscaping checks rather than school grading.

Landscape Grade Calculator method

The calculator uses metric project dimensions, applies the material formula shown below, and then adds any waste or allowance entered. Quantities are rounded up where materials are normally purchased as whole boards, sheets, blocks, rolls, bags, or packs.

grade percentage = rise / run x 100
rise = run x grade percentage / 100
angle = atan(rise / run) x 180 / pi
fall per metre in millimetres = grade percentage x 10

How to use the Landscape Grade Calculator

Choose whether you know rise and run or want to derive rise from a target grade.
Measure the horizontal run in metres.
Enter the vertical rise or fall over that run.
Review grade percentage, angle, ratio, and fall per metre.
Compare the result with drainage, path, ramp, or driveway guidance.
Get professional advice for access ramps, highways, retaining structures, or drainage-critical work.

Worked examples

Drainage fall

Input: 0.2m fall over 10m run

Calculation: 0.2 / 10 x 100

Result: A 2% grade, or about 20mm fall per metre.

Garden path

Input: Target 3% grade over 8m

Calculation: 8 x 3 / 100

Result: A 0.24m rise or fall over the full run.

When this calculator is useful

Use it before ordering materials, comparing supplier pack sizes, or checking whether a first estimate is realistic. Keep the result with your measured dimensions so you can update the calculation if the project size changes.

Inputs that affect the result

Drainage: Small grade changes can matter for surface water movement.
Accessibility: Ramp rules and practical access design can be more complex than a single slope number.
Measurement: Use horizontal run, not sloped surface length, for grade calculations.

Common mistakes to avoid

Check 1: A grade that drains water may still be unsuitable for wheelchair access.
Check 2: Driveways, public paths, and drainage systems can require professional design.
Check 3: Entering millimetres as metres will create a large error.

Material planning notes

Planning point	Why it matters
Measure finished area	Use the actual finished dimensions after allowing for openings, edges, posts, slopes, or returns.
Allow for waste	Cuts, breakages, joins, pattern matching, awkward shapes, and site handling usually mean ordering more than the exact calculated amount.
Round purchase quantities up	Most materials are bought as full boards, sheets, bags, blocks, rolls, packs, or bulk deliveries.
Check supplier specifications	Coverage, density, sheet size, block size, and pack size vary by product and supplier.

Limitations and safety

This calculator is for general project planning only. It does not replace a structural design, building regulations advice, manufacturer instructions, supplier specifications, or a competent tradesperson. Projects involving structure, roofs, retaining walls, foundations, drainage, electrics, gas, or safety-critical work should be checked properly before buying materials or starting work.

Frequently asked questions

Should I order exactly the calculated quantity?

Usually no. Order in the nearest practical pack, board, sheet, bag, roll, or delivery quantity, and keep a sensible waste allowance for cuts and mistakes.

What waste allowance should I use?

Simple rectangular jobs may only need 5-10%. Patterned, angled, fragile, or irregular projects may need more. The right allowance depends on the material and layout.

Why might my supplier quantity differ?

Suppliers use specific product sizes, densities, coverage rates, and pack quantities. Use the calculator as a planning estimate, then compare it with the product label or datasheet.

Can I use this for professional building work?

It can help with a rough take-off, but professional work should be checked against drawings, specifications, site conditions, and relevant UK rules or standards.

What measurements should I double-check?

Check length, width, depth, height, spacing, openings, pitch, and units. A small unit mistake can change a material order by a large amount.

Related calculators

roof-pitch-calculator
slope-calculator
drainage-calculator

What does this mean?

This calculator is designed to help you understand the likely number before you make a decision or start an application.

Your result should be checked against official UK guidance, especially if your circumstances include dependants, exemptions, prior leave, or a complex immigration history.

Treat the figure as a planning tool rather than legal advice. Where the answer affects an application deadline or major payment, speak to an authorised adviser.