Conversions & Units
Slope / Grade Calculator
Calculates slope as percentage, ratio, or degrees
Updated May 13, 2026 · Live
What this tool does
Calculates slope as percentage, ratio, or degrees. Drainage and ramp slopes.
Converts rise and run into slope percentage, ratio, and degrees for any grade or incline.
What this tool does not check
- Gives fall in mm only — does not size the pipe or check self-cleansing velocity.
- Does not confirm minimum/maximum gradient for your pipe diameter.
- Does not check cover depth or bedding requirements.
- Does not authorise connection to a public sewer.
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Formula Used
How the slope / grade calculator works
Calculates slope as percentage, ratio, or degrees. Drainage and ramp slopes. The calculator takes your dimensions and supplier rates, applies a standard US construction formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.
Typical US conversions and units wastage
Conversion is exact — wastage only enters when you order against the converted figure. Apply category-specific wastage to the output, not to the conversion itself. Our defaults reflect common US trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.
What this tool does not do
It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm building code compliance. Those remain the responsibility of a suitably qualified designer, engineer, or your local building official.
On-site considerations for slope / grade
US construction mixes US-customary and metric routinely (lumber sold in nominal inches but specified in actual dimensions; concrete in cubic yards but rebar in metric mass). Double-check which unit the supplier is quoting.
Codes and compliance
US building codes are published in US-customary units, with metric equivalents in parentheses. Submit plans in the unit your jurisdiction expects. When in doubt, file a pre-application question with your local building department — early clarity is cheaper than a corrective inspection.
Before you order
Note the original unit alongside the converted figure on quotes — it avoids disputes if the supplier works in the other system. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.
Adjusting the defaults
Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.
Using this slope / grade calculator alongside other BuildMetricLab tools
This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labor-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the math.
Sources & methodology
This calculator converts a slope defined by rise and run into three equivalent expressions: slope percentage (rise ÷ run × 100), slope ratio (run : rise), and angle in degrees (arctan of rise ÷ run). All three outputs describe the same incline and are derived from the same two inputs, so entering any consistent pair of rise and run values produces all three representations simultaneously. The calculator assumes rise and run are measured in the same unit, and that run is the horizontal distance rather than the slope length.
Frequently asked questions
Are slope / grade calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What is the difference between slope percentage, ratio, and degrees?
Slope percentage is rise divided by run times 100. A ratio such as 1:40 means 1 unit of rise for every 40 units of run. Degrees express the same incline as an angle from horizontal, calculated as the arctangent of rise divided by run. All three describe the same slope and can be converted between each other.
Is this a substitute for a licensed contractor or engineer?
No. This tool is a planning estimator. For work that affects structure, building code compliance, gas, electrical, plumbing, or drainage to a public sewer, consult a licensed contractor or design professional.
Does the run length need to be the actual slope length or the horizontal distance?
Enter the horizontal run, not the sloped (hypotenuse) distance. The calculator assumes the run length you enter is measured horizontally, which is standard practice for grading, ramps, and drainage falls.
Spotted something off?
Calculations or display — let us know.
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