How to Measure and Cut Stair Balusters to the Right Angle

Using a digital angle finder or a speed square, measure the angle of the underside of the handrail where the balusters will attach. This angle is critical for ensuring the balusters sit flush against the handrail and the tread or riser. Record this measurement precisely. If using a speed square, you may need to transfer the angle to a protractor for a more accurate reading. For a consistent angle across all balusters, consider using a jig or a consistent reference point.

Once the stair slope angle is determined, you can calculate the required length of each baluster. Measure the vertical distance from the top of the tread or the riser to the underside of the handrail. Subtract the space needed for the baluster shoe or mounting bracket from this measurement. For angled cuts, the length will be the hypotenuse of a right triangle where one leg is the vertical rise and the other leg is the horizontal run, adjusted by the angle of the handrail. Alternatively, hold a tape measure vertically from the tread/riser to the handrail, then pivot it to match the handrail's angle and read the length. Ensure this calculation accounts for any bottom connectors or shoes.

Based on the measured stair slope angle, set your miter saw or circular saw to the corresponding angle. If your baluster will attach to a flat tread and a sloped handrail, you will need to set a compound angle. Typically, this involves setting the miter angle to match the slope of the handrail and the bevel angle to create the necessary angle on the end of the baluster. Consult your saw's manual for setting compound angles. Ensure the saw is securely set and locked at the desired angle.

Mark the determined length on each baluster. Place the baluster on the saw, ensuring it is securely clamped and aligned with your cut marks. Make the first angled cut. Carefully measure and mark the final length from the apex of the first cut. Position the baluster for the second angled cut, ensuring the angle corresponds to the angle of the tread or riser it will sit on. Execute the second cut. Repeat this process for all balusters, ensuring consistency in length and angle for each pair that attaches to the same stair.

Before permanent installation, place each cut baluster in its intended position without adhesive or fasteners. Check that the top of the baluster sits flush against the underside of the handrail and the bottom rests securely on the tread or riser. Ensure there are no gaps and that the baluster is plumb (if applicable) and stable. Make any necessary minor adjustments by slightly trimming an angle or length if a baluster is slightly off. This step is crucial to avoid costly mistakes during final installation.