Patios

Concrete Patio Slope

Calculate patio slope from rise and horizontal run. Check running slope, cross slope, doorway levels and the complete water route.

Calculate measured slope

Enter both measurements. Slope is geometry, not approval of a design.

Manual method: rise in inches divided by run in feet divided by 12, then multiplied by 100 gives percent slope. Use horizontal run. Measure running slope and cross slope separately.

Residential patio beside a planted edge

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Concrete patio slope is a geometry question and a site-design question. The worksheet above answers the geometry part. Measure the rise and horizontal run, then check the result against the actual water route and project requirements.

Calculate patio slope by dividing vertical rise by horizontal run in matching units, then multiply by 100 for percent. A 3-inch change over 25 feet is 1 percent; 6 inches is 2 percent. Those examples are not universal design targets. Check the doorway contact and complete outlet route. One measured line cannot prove that the whole patio drains, and the worksheet cannot approve a local grade or accessible-route detail.

Concrete patio slope calculation

For a rise measured in inches and a horizontal run measured in feet:

Slope percent = rise in inches ÷ (run in feet × 12) × 100.

The factor of 12 puts both measurements in inches. If the measurements already use the same unit, divide rise directly by run. Do not mix a rise in inches with a run in feet without the conversion.

Measured example Slope Equivalent ratio
3-inch rise over 25 horizontal feet 1 percent 1:100
6-inch rise over 25 horizontal feet 2 percent 1:50
12-inch rise over 25 horizontal feet 4 percent 1:25
12-inch rise over 20 horizontal feet 5 percent 1:20

These are arithmetic examples. They do not select a target for your patio or establish a legal limit. A desired grade must be assessed with the site and intended use.

Return to the patio cost guide when the layout is defined. Drainage work can be a separate scope from the new surface. Keep unpriced corrections visible in the estimate.

Measure rise between defined points

Choose two points and record their locations. The rise is their vertical height difference. Use a suitable measurement method for the site and retain its units.

Do not infer rise from the apparent angle in a phone photo. Perspective can make a level surface look sloped. A photo is useful for identifying the points, while the measurement supplies the number.

If the result is based on provisional levels, label them as provisional. An input of zero is a measured zero only when that is what you found. Missing rise should not be entered as zero to make the form run.

Keep the measurement direction clear. A numerical rise describes magnitude. Record which end is higher so the water-route plan can use the result correctly.

Use horizontal run

The run is horizontal distance between the defined points. It is not automatically the distance measured along a sloping face. Use a method that gives the intended horizontal measurement.

For a simple level-based measurement, record the span and endpoints. If the patio shape is complex, break the layout into defined runs. Avoid assigning one convenient distance to every edge.

Use consistent units. A metric measurement can be calculated with matching rise and run units. If entering the inch-and-foot worksheet, convert carefully and retain the original record.

The concrete calculator also relies on clear units for area and volume. Quantity arithmetic and grade arithmetic answer different questions. A correct area result does not prove the measured slope.

What a percentage means

One percent means one unit of vertical change for every hundred matching units of horizontal run. Two percent means two for every hundred. It is not the same as an angle of one or two degrees.

Ratios give another way to express the same geometry. At 2 percent, the ratio is 1:50. The display uses that ratio to describe the entered measurements, not to approve them.

If someone specifies a target as a percentage, keep that wording on the plan. Do not change it into degrees without a correct conversion. If the notation is unclear, resolve it before setting forms.

The worksheet reports the entered line. It cannot identify whether that line is the main water route. The drawing needs to show the direction alongside the number.

Doorway and house contacts

Record the finished surface contact at the doorway. Include any step or adjoining path. The grade must fit those contacts as well as the intended outlet.

Do not raise or lower one edge based solely on a generic percentage. That change can affect the door or another route. Ask the actual plan to show the resulting levels.

If the patio sits between fixed surfaces, measure both contacts. A simple uniform plane may not fit them. The design may need another detail rather than a guessed adjustment at one corner.

Read patio installation planning for the sequence of level checks before placing. A surface finish cannot correct a contact detail that was never resolved.

Main grade and cross slope

A patio can have grade in more than one direction. A line toward the outlet may be the main run. A line across it describes a different part of the surface.

Measure and label both where needed. The same patio can show a useful slope along one line and a low point off that line. One endpoint calculation cannot establish a complete surface model.

For a route used by people, its grade and contacts may also have access requirements. Identify the actual route and governing project scope. Public sidewalk standards should not be applied automatically to every private patio.

The U.S. Access Board's public right-of-way guidance concerns that defined setting. It is a useful reminder to check scope before borrowing a number.

This page does not declare a private patio compliant from one worksheet result.

A plane is different from a path with low points

Imagine two endpoints with a 6-inch difference over 25 feet. The calculated line slope is 2 percent. The surface between them may still dip and rise.

In that case, the same endpoint result does not prove that water moves across the full run. Record intermediate levels when the assessment needs them. A local low point can remain even with a positive overall fall.

For an existing patio, observe water after rain. Mark where it gathers and where it exits. The observation can guide measurements, but it does not alone diagnose why the surface settled.

If a new patio has a complex shape, keep all critical levels on the plan. Do not assume each leg follows the same plane. The patio ideas guide helps keep the layout and use connected.

The outlet is part of drainage

A patio grade needs somewhere suitable for water to go. Show the complete route beyond the surface edge. Water leaving the concrete is not automatically resolved if it then pools beside the home.

Check any local discharge requirements that apply. Keep nearby property and public contacts in the assessment. This guide cannot choose an outlet from the measured percentage alone.

If a drain is proposed, record its complete scope. Include its connection and discharge route. A channel body at a low point is only one part of the system.

Keep drainage pricing separate when the patio package excludes it. A low installed surface allowance cannot establish the price of a working outlet. Leave that cost unknown until the actual work is described.

Turning a target into a height difference

If a project plan already states a target percentage, arithmetic can show the corresponding rise. Multiply horizontal run by the decimal form of the percentage. Keep the units matched.

For illustration, a stated 2-percent line over 25 feet needs a 0.5-foot vertical change, which is 6 inches. That is a calculation of a stated target. It is not this site's recommendation to use that grade.

Check both endpoint levels after doing the math. The proposed rise must fit the doorway and outlet. If it does not, the design question remains open even though the multiplication is correct.

Retain the source of the target on the drawing. It may come from a site plan or an applicable requirement. A number copied from an unrelated yard should not be treated as that source.

Measurement uncertainty

Small differences in measured rise can change the percentage. Keep the precision of the result consistent with the input. A display with extra decimals does not make a rough measurement exact.

For example, measurements around the same 25-foot run may give different rise readings at nearby points. Record which points were used. Do not average them silently if the layout includes a local low spot.

If the measured run is wrong, even a precise rise produces a misleading slope. Check the horizontal basis and unit conversion together. This is why the worksheet preserves entered inputs with the result.

When a decision depends on a tight requirement, use the project's appropriate survey and review process. An informal estimate is useful for planning. It should remain labeled as such.

Use, reset and print the worksheet

Enter the measured rise and horizontal run in the labeled fields. A missing or invalid input returns an error instead of a grade. Review the input named in the message.

The slope updates when both measurements are valid. Clearing a required measurement hides the previous answer so an earlier result cannot stand in for the new input. Your measurements are saved on this device when browser storage is available.

The print view retains the measured values and method limits. It is a geometry record. It does not become a design approval when printed.

Without JavaScript, the page shows the formula for manual calculation. Keep the same units and record the endpoints. The arithmetic method is unchanged even when the interactive control is unavailable.

Finish and joints do not select grade

A patterned or rough surface still needs the actual levels and water route. Choose the patio finish after the grade plan is clear. A texture category cannot prove that water leaves a low point.

NRMCA CIP 6 explains functional slab joints. They belong beside the finish plan. A decorative groove should not be treated as a drainage channel without an actual designed scope.

Keep the slab thickness separate too. Grade describes level change; thickness describes the concrete section. Raising a surface and thickening a slab are different changes to the plan.

New and existing patios

For a new patio, resolve levels before placing. Record the contact points and the approved outlet. The installer needs a clear plan rather than a general request to make water run away.

For an existing patio, retain measured facts and observed ponding. Ask an assessor to identify the cause before choosing a treatment. A coating does not change the underlying geometry simply because it makes water bead.

Compare a defined repair with replacement where appropriate. Keep the height consequences of each option visible. An added layer can change the doorway contact even if it improves one low area.

What the slope result can tell you

The worksheet calculates rise over horizontal run. Use it to record measured geometry; it does not model surface flow or certify an accessible route.

NRMCA provides joint guidance, while Access Board material applies within its stated scope. Local design and outlet approval remain project-specific.

Keep a repeatable measurement record

Mark the same endpoints when checking the patio again. A new reading from another pair of points describes another line. It should not be presented as change over time without that distinction.

Keep the measuring method and original units with the date. Note any rough edge or contact that made the reading uncertain. The result can then be assessed with its limits intact.

If ponding appears elsewhere, add a new labeled measurement. Do not overwrite the first line simply to obtain a more favorable percentage. A useful record shows both the original run and the newly observed area.

FAQ

What slope should a concrete patio have?

Use a suitable site plan and any requirements that apply to the actual patio and route. This worksheet does not select a universal target. Measure the doorway contact and complete water route.

A general percentage cannot establish that those levels fit or that the discharge location is acceptable at your property.

Is two percent the same as two degrees?

No. Percent slope is rise divided by horizontal run, multiplied by 100. Degrees describe an angle and use another conversion.

Keep the specified notation clear before measuring or setting levels. The example 2-percent line over 25 feet has a 6-inch rise; it is not an angle of two degrees.

Does one slope reading prove the patio drains?

No. It describes the line between the entered points. A low spot elsewhere or between them may still retain water.

Record the broader levels and observed route where needed. The outlet also matters, so a correct rise-over-run result cannot alone establish complete drainage or approve the finished surface.

Can a new sealer fix a low spot?

A coating does not automatically change slab geometry. Identify the cause and assess a suitable repair scope. Keep any added layer's height effects visible at doors and adjoining routes.

Do not choose from a promise that a shinier or water-beading surface resolves the actual level and outlet problem.

Can I use sidewalk rules for a private patio?

Check the actual scope first. Public right-of-way guidance addresses a defined setting and should not be copied as a universal private-patio rule. Identify the relevant site and route requirements with the responsible authority.

The worksheet gives geometry only; it cannot certify compliance from the entered rise and run.

Verdict on concrete patio slope

Calculate concrete patio slope from clear measurements and matching units. Keep the endpoints and direction on the plan. Check the full water route and fixed contacts before choosing a target. A useful percentage supports the design record, while the actual drainage and access decisions still need their project scope.