# Slope Calculator Calculate slope from two points, rise and run, missing values, or project run and fall. Live diagram, four formats, per-field units. Canonical page: https://invoicemama.com/calculators/slope-calculator This is a free browser calculator. Treat results as planning aids and confirm figures against your own measurements, codes, and professional judgment. ## How to calculate slope with this tool Pick a solve mode, enter the measurements you know, and read slope in ratio, percent, degrees, and per mille at once. ### 1. Select your solve mode Choose two points, rise and run, find a missing dimension, or project run/fall for site work. The mode switcher at the top sets which inputs appear. ### 2. Enter known values and units Type coordinates, rise, run, fall, or slope in the units you measured on site. Pick millimeters, feet, meters, or other units per field without converting manually. ### 3. Read slope in all four formats Results update live in ratio (1:X), percent grade, degrees, and per mille. Edit any format field to convert the others instantly, then copy or share the link. ## Frequently asked questions ### How do I calculate slope between two points? Subtract the y-values and divide by the difference in x-values: m = (y₂ − y₁) / (x₂ − x₁). That rise-over-run ratio is your slope. Enter both points in our two-point mode and you get slope, angle, distance, and all four format outputs without rearranging the formula yourself. ### How do I convert slope percentage to degrees? Treat percent as rise per hundred units of run: slope m = percent / 100. Then degrees = atan(m) x (180/π). Example: 10% -> m = 0.1 -> about 5.71°. Type 10 in the percent field here and the degree box updates automatically, or use the slope to angle chart below. ### What does a 1:100 slope mean? A 1:100 slope rises 1 unit vertically for every 100 units horizontally. That equals 1% grade, 10‰, or roughly 0.57°. It is a common minimum for surface drainage and gentle ramps. Enter 100 in the ratio field (as X in 1:X) to see the matching percent and degrees. ### What is the maximum slope for a wheelchair ramp? In many US accessibility guides the steepest allowed running slope is 1:12 (8.33%). Some jurisdictions allow 1:10 for short rises only. Always check your local building code and landings at the top and bottom. Use ramp project hints here, then confirm with the authority having jurisdiction. ### What slope is required for stormwater drainage? Open swales often target 0.5% to 2% (1:200 to 1:50). Buried storm pipes frequently need at least 1% (1:100) so solids do not settle. Steeper is not always better if erosion becomes a problem. Our drainage project hint shows typical ranges; your engineer or municipality sets the final number. ### How do I calculate the rise from a known run and slope? Multiply run by the slope ratio: rise = run x (rise/run). If you know percent, rise = run x (percent / 100). If you know degrees, rise = run x tan(angle). Project run/fall mode does this for you: enter horizontal run and target slope to get vertical fall instantly. ### What is the difference between slope ratio and slope percentage? Ratio is written 1:X where X is how much horizontal run matches one unit of rise (or the inverse depending on convention). Percent is rise divided by run, times 100. A 1:50 ratio equals 2% because 1/50 = 0.02. Both describe the same steepness; contractors often use ratio for drains and percent for roads. ### How steep is a 10% slope? Ten percent means 10 units of rise per 100 units of run, a ratio of 1:10 and about 5.71°. Walking feels noticeably uphill; vehicles handle it on driveways but you may need traction in ice. It is steeper than typical ADA ramps (8.33% max) but common on residential streets in hilly areas. ### What is the slope of a horizontal line? A perfectly flat horizontal line has zero slope because rise is zero while run can be any nonzero value. The angle is 0° and percent grade is 0%. Vertical lines are different: run is zero so slope is undefined, not zero. Our calculator explains which case you hit with plain-English messages. ### How do I calculate slope for a roof? Roof pitch is still rise over run, usually quoted as inches of rise per 12 inches of run (such as 6:12). Measure vertical rise and horizontal run along the roof plane, enter them in rise and run mode, and read percent or degrees. For preset x:12 conversions, try our roof pitch calculator too. ## Turn Grade Checks Into Paid Invoices You verified the slope on site. Invoice Mama helps contractors and landscapers turn those measurements into professional estimates and invoices in minutes. - [Create your first invoice free](https://app.invoicemama.com/sign-up) --- Invoice Mama is invoicing software for contractors, freelancers, and small businesses. 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