Use this Inch Per Foot Slope Calculator to find slope from total rise and run, or calculate total rise or total run from a known slope. It also converts inches per foot into percent grade and angle in degrees.
Formulas & Rules
An inch per foot slope measures the vertical inches of rise or fall for each 1 foot of horizontal run. This calculator helps you quickly find that exact measurement.
You can use this tool to calculate your slope in inches per foot by entering the total rise and total run. You can also work backward to calculate the total rise if you know the slope and run, or find the total run if you know the slope and rise. Along with these primary results, the tool automatically translates your slope into a percentage and an angle in degrees.
To ensure the math is always correct for your project, the inputs and outputs use specific units: you enter or receive the rise in inches, the run in feet, the slope in in/ft, the percent in %, and the angle in degrees.
What this inch per foot slope calculator calculates
The tool provides three distinct calculation paths depending on the measurements you already have.
| Calculation method | Inputs | Outputs | Tool rule |
|---|---|---|---|
| Calculate slope from rise and run | Total Rise (in), Total Run (ft) | Slope (in/ft), Slope Percentage (%), Angle (deg) | Run must be greater than 0 |
| Calculate total rise from slope and run | Slope (in/ft), Total Run (ft) | Total Rise (in), Total Rise (ft), Angle (deg) | Zero slope is allowed |
| Calculate total run from slope and rise | Slope (in/ft), Total Rise (in) | Total Run (ft), Total Run (in), Angle (deg) | Slope must be greater than 0 |
Inch per foot slope formula and conversion formulas
Finding the slope requires a straightforward division, but converting that result into a percentage or an angle requires accounting for the difference in units. Because the rise is in inches and the run is in feet, percent and angle conversions must account for 12 inches per foot. This tool handles these conversions automatically using the formulas below.
The core equation for slope is:$$\text{Slope (in/ft)} = \frac{\text{Rise (in)}}{\text{Run (ft)}}$$
To find the slope as a percentage:$$\text{Slope \%} = \left( \frac{\text{Rise (in)}}{\text{Run (ft)} \times 12} \right) \times 100$$
To find the angle in degrees:$$\text{Angle (deg)} = \arctan\left( \frac{\text{Rise}}{\text{Run} \times 12} \right) \times \frac{180}{\pi}$$
If you need to work backward from a known slope, the calculator uses these reverse formulas:$$\text{Total Rise (in)} = \text{Slope (in/ft)} \times \text{Total Run (ft)}$$$$\text{Total Rise (ft)} = \frac{\text{Total Rise (in)}}{12}$$$$\text{Total Run (ft)} = \frac{\text{Rise (in)}}{\text{Slope (in/ft)}}$$$$\text{Total Run (in)} = \text{Total Run (ft)} \times 12$$$$\text{Angle (deg) from slope} = \arctan\left( \frac{\text{Slope}}{12} \right) \times \frac{180}{\pi}$$
How to calculate inches per foot slope from rise and run
Finding your slope manually is a simple process of gathering your two main measurements and dividing them.
First, measure the total vertical rise or fall in inches. Next, measure the total horizontal run in feet. Divide your rise by your run to get the slope in inches per foot. You can then use those same values to convert the result into a percent and angle if needed.
| Total Rise (in) | Total Run (ft) | Slope (in/ft) | Slope % | Angle (deg) |
|---|---|---|---|---|
| 6 | 24 | 0.25 | 2.08% | 1.19° |
Convert inches per foot slope to percent grade and degrees
It is very common to need a slope expressed in different formats. A crucial thing to remember is that 1 in/ft does not mean 1%. It actually equals 8.33% because 1 foot contains 12 inches. The tool calculates these equivalents for you instantly.
| Slope (in/ft) | Percent Grade | Degrees |
|---|---|---|
| 0.125 | 1.04% | 0.60° |
| 0.25 | 2.08% | 1.19° |
| 0.5 | 4.17% | 2.39° |
| 1 | 8.33% | 4.76° |
| 2 | 16.67% | 9.46° |
| 3 | 25.00% | 14.04° |
| 4 | 33.33% | 18.43° |
| 6 | 50.00% | 26.57° |
| 12 | 100.00% | 45.00° |
Common inch per foot slope conversions table
For quick lookups, you can use this reference table. It covers the most frequent fractional inch slopes and shows their exact decimal, percentage, and degree equivalents.
| Inches per Foot | Decimal in/ft | Percent Grade | Degrees |
|---|---|---|---|
| 1/16 in/ft | 0.0625 | 0.52% | 0.30° |
| 1/8 in/ft | 0.1250 | 1.04% | 0.60° |
| 3/16 in/ft | 0.1875 | 1.56% | 0.90° |
| 1/4 in/ft | 0.2500 | 2.08% | 1.19° |
| 3/8 in/ft | 0.3750 | 3.13% | 1.79° |
| 1/2 in/ft | 0.5000 | 4.17% | 2.39° |
| 3/4 in/ft | 0.7500 | 6.25% | 3.58° |
| 1 in/ft | 1.0000 | 8.33% | 4.76° |
| 2 in/ft | 2.0000 | 16.67% | 9.46° |
| 4 in/ft | 4.0000 | 33.33% | 18.43° |
| 6 in/ft | 6.0000 | 50.00% | 26.57° |
| 12 in/ft | 12.0000 | 100.00% | 45.00° |
Calculate total rise from slope and run
If you already know the slope requirement in inches per foot and the total horizontal run in feet, the tool will calculate the total vertical rise for you.
When using this mode, the calculator provides your total rise in both inches and feet. It also outputs the corresponding angle in degrees for your reference.
| Slope (in/ft) | Total Run (ft) | Total Rise (in) | Total Rise (ft) | Angle (deg) |
|---|---|---|---|---|
| 0.25 | 24 | 6 | 0.5 | 1.19° |
| 0.5 | 40 | 20 | 1.667 | 2.39° |
| 1 | 12 | 12 | 1 | 4.76° |
Calculate total run from slope and rise
If you know the target slope in inches per foot and your total vertical rise in inches, the tool can figure out how much horizontal space you need.
In this mode, the calculator returns your total horizontal run in both feet and inches. Just like the other calculation paths, it also displays the angle in degrees.
| Slope (in/ft) | Total Rise (in) | Total Run (ft) | Total Run (in) | Angle (deg) |
|---|---|---|---|---|
| 0.25 | 6 | 24 | 288 | 1.19° |
| 0.5 | 12 | 24 | 288 | 2.39° |
| 2 | 18 | 9 | 108 | 9.46° |
What the results mean in inches per foot
Because the tool provides multiple types of results at once, it helps to understand exactly what each number represents. A slope of 0 in/ft is completely flat. The calculator allows a zero slope in rise mode, but not in run mode, because dividing a rise by a zero slope would not produce a finite horizontal run.
| Output | Meaning | Why it matters |
|---|---|---|
| Slope (in/ft) | Vertical inches of rise or fall for every 1 foot of horizontal run | Primary format for this calculator |
| Slope Percentage (%) | Rise divided by run after converting feet to inches | Useful when users compare grade values |
| Angle (deg) | Arctangent-based angle of the slope | Useful when slope must be expressed as degrees |
Input limits and calculator rules
To keep the math accurate and prevent impossible calculations, the tool follows a few specific rules regarding what numbers you can enter.
| Rule | Behavior in this calculator |
|---|---|
| Negative values | Not allowed |
| Run = 0 in slope mode | Shows validation error |
| Slope = 0 in run mode | Shows validation error |
| Slope = 0 in rise mode | Allowed; returns 0 rise and 0° |
| Very steep slopes above 3 in/ft | Warning shown |
| Slopes above 12 in/ft | Stronger steepness warning shown |
Common inch per foot slope examples
Here are a few standard examples showing how common fractional slopes translate into percentages and degrees.
| Example slope | In/ft | Percent | Degrees |
|---|---|---|---|
| Flat surface | 0 | 0% | 0° |
| 1/8 inch per foot slope | 0.125 | 1.04% | 0.60° |
| 1/4 inch per foot slope | 0.25 | 2.08% | 1.19° |
| 1/2 inch per foot slope | 0.5 | 4.17% | 2.39° |
| 1 inch per foot slope | 1 | 8.33% | 4.76° |
Inch per foot slope vs percent grade
An inch per foot measurement is a construction-style way to express a slope, while a percent grade is the exact same rise and run relationship expressed as a percentage.
Because the run in this context is measured in feet and the rise is measured in inches, simply multiplying your in/ft value by 100 is not the correct way to find the percent. The correct relationship requires dividing by 12 first. The formula is percent grade = (in/ft ÷ 12) × 100, which means 1 in/ft equals 8.33%.
| Inches per Foot | Percent Grade |
|---|---|
| 0.125 | 1.04% |
| 0.25 | 2.08% |
| 0.5 | 4.17% |
| 1 | 8.33% |
| 2 | 16.67% |
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