Countertop Calculator
Calculate countertop square footage, material allowance, backsplash area, and preliminary project cost using a live floor-plan diagram.
Informational estimate only. Confirm final measurements, seams, slab needs and quotes with your fabricator. Terms and Conditions
Measure finished outside dimensions. Joined runs deduct shared corners exactly once.
Measure your countertops
Enter finished outside dimensions, including overhang. L/U layouts use full outside leg lengths; shared corners count once.
Countertop area & estimate
Finished area first. Purchasing allowances and cost are separate estimates.
Project quantities and cost
Show calculation stepsDimensions, overlaps, cutouts, cost and assumptions
- Enter valid dimensions to see the calculation.
Your countertop floor plan
Scaled top view of finished outside dimensions. The selected shape is shown below; section measurements remain in text for accessibility.
Blue = countertop runs · Orange dashed = rectangular opening in first run · Green = separate island. Geometry scales to measurements; narrow pieces can become too small to see. Not a fabrication drawing.
Method, sources & assumptions
Geometric area is exact for the entered simplified shape; purchasing and pricing are preliminary estimates.
Finished plan area is computed using rectangle union and shared-corner subtraction. Conversion uses 1 in = 0.0254 m (exact).
- Example: 120 × 25.5 in wall counter, 10% optional planning allowance, illustrative $65/sq ft installed rate (not a market quote).
- Cutouts reduce net visible surface but do not automatically reduce billed area, purchase quantity or slab requirements.
- A matching-material backsplash is included in planning area and the area-based quoted price. Installed-price mode does not add the planning allowance to billable area; material-only mode does. Waste is not a verified nesting plan.
- No slab count, piece nesting, seam placement, material-specific cost, support strength, code compliance or vendor quote is determined by this calculator. Confirm final fabrication and applicable taxes with professionals.
Measurement and estimating guide
Countertop Calculator Guide
To calculate countertop square footage, measure the finished length and depth of each section, multiply them, divide by 144 when measuring in inches, and add the non-overlapping section areas. The calculator above handles straight, L-shaped, and U-shaped layouts and shows finished countertop area along with optional material, edge, backsplash, and cost estimates.
For connected runs measured using full outside dimensions, a shared corner must be counted only once. Your finished surface area is not necessarily the quantity of raw material you must buy or the area your supplier will bill.
- Measure
- Finished length and depth of each run
- Main result
- Finished countertop area in ft² or m²
- Before ordering
- Verify the slab layout and supplier quote
How to Measure and Use the Calculator
Start with a simple overhead sketch of your kitchen and record the finished outside dimensions, not only the cabinet footprints. Include any planned overhangs in the measurements once.
Choose the layout and measurement units
Select Straight, L-shaped, or U-shaped and choose inches, centimeters, or millimeters. For L- and U-shaped layouts, measure each connected leg using its full outside length, including the shared corner. Changing the unit selector converts the existing measurements rather than changing the physical countertop size.
Enter the finished length and depth of each run
Measure from the intended finished countertop edges. Record the front-to-back depth including the front overhang and any other included extension. An island or peninsula can be entered separately using its own finished length and depth.
Enable only the optional features that apply
The calculator can include a separate rectangular island, one rectangular sink or cooktop opening, and a matching-material rectangular backsplash. Record each opening and backsplash separately; do not subtract a sink opening from the gross countertop measurement yourself.
Check the diagram and choose the pricing basis
Compare the diagram’s section dimensions against your sketch. If estimating cost, use your supplier’s actual quote and choose either installed price per square foot or material price per square foot plus separately charged labor. The displayed floor plan is a preliminary measurement aid, not a fabrication template.
Countertop Square Footage Formulas
For any rectangular countertop section measured in inches, multiply the finished length by the finished depth, then divide by 144 to convert square inches to square feet.
Rectangular countertop area
Area in ft² = finished length in inches × finished depth in inches ÷ 144.
The divisor is exact because 12 inches × 12 inches = 144 square inches per square foot. This formula applies to one rectangular surface; connected rectangles require shared areas to be counted once.
- \(A\)
- Finished countertop areaHorizontal surface area of the rectangular section.
- \(L\)
- Finished lengthOutside length of the countertop section, including the planned finished end extensions.
- \(D\)
- Finished depthOutside front-to-back measurement of the surface, including the planned overhang.
Square feet versus linear feet
Linear feet describe the length of a countertop run or a finished edge, while square feet describe the surface area. A 10 ft long countertop is not automatically 10 ft²: at a finished depth of 25.5 in, its area is 21.25 ft².
Using metric measurements
When both measurements are in meters, multiply length by depth to obtain m². When both are in millimeters, divide their product by 1,000,000. One ft² is exactly 0.09290304 m². Changing the calculator’s area-display selector changes the displayed unit, not the physical area.
Worked Kitchen Countertop Example
Consider a kitchen with two perpendicular wall runs measured by their full outside lengths, plus a separate rectangular island. Both wall runs are 25.5 in deep; their common corner must be subtracted once.
Calculate each wall run
Subtract the common corner and add the island
Result
58.23 ft² of finished countertop surface
Use this as the preliminary finished surface area of the two joined wall runs and separate island, before any optional backsplash or material purchasing allowance.
L-Shaped, U-Shaped, and Island Layouts
When multiple rectangular runs join, measure the same finished geometry consistently. If every full outside leg includes the common corner, add the rectangles and deduct their actual intersection once.
L-shaped kitchen: one shared corner
For perpendicular full outside leg measurements, an L-shaped plan has the first run area plus the second run area minus the corner counted in both. With 120 in and 96 in legs of equal 25.5 in depth, the area is 33.73 ft². If you already divided the L into non-overlapping pieces, add those piece areas instead and do not deduct the corner again.
U-shaped kitchen: two shared corners
A conventional U-shaped counter has three joined rectangular runs. Add their individual rectangular areas and subtract the two distinct corner intersections. For a 120 in rear run and two 96 in side runs, all 25.5 in deep, the total is 46.22 ft² when both corner overlaps are 25.5 × 25.5 in and do not overlap each other.
U-shaped example
Three rectangular run areas, minus both distinct shared corners, equal 46.22 ft² after rounding.
This simplified calculation assumes perpendicular runs and two separate shared corners. Offset, angled, curved, or unusually narrow layouts require a takeoff based on their actual geometry.
Separate island or peninsula
Calculate a free-standing rectangular island independently using its finished top dimensions. An 84 × 42 in island adds 24.50 ft². The finished top may be larger than the cabinet footprint because of seating or edge overhangs; the area calculation does not verify the adequacy of that overhang’s support.
Understanding Your Area and Material Results
The finished surface area, cutout-adjusted surface area, planning quantity, and purchased stock are different measures. Treat them separately when comparing your calculator result with a supplier quote.
Finished surface area
The gross horizontal area of the modeled countertop runs and optional island. Use it to compare the intended dimensions and layout with your measurement sketch.
Cutout-adjusted area
A rectangular sink or cooktop opening can reduce net remaining surface, but the removed piece may not reduce a supplier’s billed area or raw slab purchase.
Material planning quantity
An optional allowance increases the area-based planning quantity. It does not prove that each cut piece fits within available slabs or panels.
Example: Why one project has several different areas
For a hypothetical 40 ft² finished countertop with a 3 ft² opening, the net remaining surface is 37 ft². A separate 10% planning allowance applied to the gross 40 ft² produces 44 ft² of area-based planning material. Neither number establishes the fabricator’s billable area or exact raw stock requirement.
Gross versus net
Gross: 40 ft². Net after the opening: 37 ft². A cutout can reduce net surface without reducing the raw piece required for fabrication.
Planning versus ordering
At 10% allowance: 44 ft² of illustrative planning quantity. Verify actual slab or panel sizes, orientation, usable margins, seams, and cutout placement before purchasing.
Estimating Countertop Cost and Finished Edges
A useful preliminary cost estimate starts with the supplier’s actual price basis. An installed square-foot rate and a material-only square-foot rate are not interchangeable.
Installed price per square foot
Multiply the supplier’s billable area by the quoted installed rate. Add only specifically excluded services; do not add labor or fabrication a second time if they are already included.
Material price plus labor
Use the supplier’s material price and the applicable material quantity basis, then add separately quoted labor and other excluded items. The calculator’s area-based allowance is a planning estimate, not proof of slab yield.
For illustration, 40 ft² at a hypothetical $65 per installed ft² produces a $2,600 base area charge. This rate is not a current market quote. Actual pricing may depend on the selected product, supplier minimums, fabrication, backsplash, edge profile, delivery, removal, and plumbing work.
Finished edges use linear feet, not square feet
A wall run may need its front edge and any exposed ends finished; an independent island may have four exposed edges. The full perimeter of an 84 × 42 in rectangular island is 21 linear ft, calculated as 2 × (84 + 42) ÷ 12. Confirm which edges are exposed and which edge services the quote includes.
Different materials have different purchase constraints
Quartz and natural stone may be priced using slab purchasing and fabrication requirements. Laminate and butcher block may involve stock lengths, sheets, or panels. Concrete may require a volume-based materials estimate. Choose the appropriate supplier pricing method rather than assuming every material can be ordered as an exact number of finished square feet.
Measurement Mistakes and Final Checks
Most useful corrections happen before purchasing: confirm the measurement convention, include all intended finished extensions, and distinguish the calculator’s planning geometry from a fabricator’s final measurements.
Corner counted twice
For full outside L- or U-shaped leg measurements, subtract each shared intersection once. If you measured separate non-overlapping rectangles already, do not subtract a corner again.
Overhang omitted or added twice
Enter finished outside length and depth. Cabinet dimensions alone may miss the overhang, while adding it again to finished dimensions overstates area.
Sink cutout treated as purchased-material savings
Record net surface separately. A fabricator may still need the full stock piece around the opening, and the supplier may not deduct the opening from the billed area.
Area estimate treated as a cutting plan
Check each planned piece against actual stock length and width. The area total alone cannot establish seam positions, material grain or vein orientation, saw kerf, or the number of slabs.
Countertop Calculator FAQs
How many square feet is a 10-foot countertop?
At 25.5 in finished depth, a 10 ft (120 in) countertop has 120 × 25.5 ÷ 144 = 21.25 ft². A different depth gives a different area.
Should a countertop overhang be included in square footage?
Yes. Use the planned finished outside dimensions including the overhang. If your entered dimensions already include it, do not add it again.
Does backsplash area count toward countertop material?
Calculate vertical backsplash area separately. A matching-material backsplash can increase the planning requirement for that material; a tile backsplash needs its own material takeoff.
Does a sink opening reduce the slab quantity or quoted cost?
Not necessarily. The opening reduces net remaining surface but may not reduce the full cut piece, slab purchase, or the supplier’s billable area. Confirm the supplier’s method.
How much extra countertop material should I allow for waste?
No single percentage guarantees a particular project will fit available stock. Use an explicit planning allowance for a rough estimate and confirm the actual piece layout with your fabricator.
Can this calculator determine exactly how many stone slabs to buy?
No. Exact slab purchasing requires actual stock and cut-piece dimensions, seam and pattern constraints, usable margins, and a verified fabrication plan.