This is a circular slide rule simulator. Use the mouse wheel while you have your mouse outside of the face to move the hand (needle). Using the wheel inside the face moves the dial.

For precise adjustments, use the Fine Mode toggle button or hold Shift key while moving. Click outside the face to align the dial with the needle, and click again to align with the index mark. Click inside the face to align the needle with the dial's index.

On mobile devices, you can toggle between Scrub Mode (default vertical scrolling) and Drag Mode (circular dragging). In Drag Mode, touches near the needle will move the needle, while touches elsewhere will move the dial.

Different scales are available through the dropdown menu in the controls section:

• C/D Standard: Basic logarithmic scale for multiplication and division
• A/B Square: Squared values (x²) for squares, square roots, and area calculations
• K Cube: Cubed values (x³) for volumes and cube roots
• L Logarithm: Directly shows base-10 logarithms
• S Sine: Logarithmic sine function (range 6°-90°)
• T Tangent: Logarithmic tangent function (range 6°-45°)
• ST Small Angle: Small angle scale (0°-6°) where sin(θ) ≈ tan(θ) ≈ θ radians
• CI Reciprocal: Reciprocal values (1/x) for division and reciprocals

The gauge marks are as follows: π ~ 3.1416, e ~ 2.71828, c ~ 1.128 marks sqrt(4/pi) for finding circle areas given their diameter, L marks ln(10) ~ 2.3026, r ~ 57.3 is degrees in a radian, and Q ~ 0.01745 is radians in a degree. (Special marks vary depending on the selected scale.)