Projected Area Calculator

Calculate the mold-opening projection from rectangle dimensions, a circle diameter, or a known CAD area. Include identical cavities and the complete runner/feed system, then read the total in cm² and in² for clamp-force planning.

Formula and method

Total projected area = per-cavity area × identical cavities + complete feed-system area.

Rectangle: A = length × width. Circle: A = π × diameter² ÷ 4. Known/CAD mode uses the entered per-cavity projection directly. Dimensions in mm are converted to cm before calculating area; 1 in² = 6.4516 cm².

Inputs and units

View the cavity along the mold-opening/clamp direction. Use mm with cm² or inches with in². Changing the unit selector converts the current dimensions and area values rather than changing their physical meaning. Use a positive whole number of identical cavities; enter the complete feed-system projection once, including relevant cold runners, sprue, cold wells, and wide gates.

Worked example

One 120 × 80 mm rectangular projection is 96 cm². Two identical cavities plus 12 cm² of feed system give 204 cm², or 31.620 in². A 100 mm circular projection is 78.54 cm² per cavity; at two cavities with 12 cm² feed system, the total is 169.08 cm².

Choose the projection, not the surface area

A projected area is the two-dimensional silhouette seen along mold opening. It is not total 3D surface area, wall cross-section, resin volume, or runner volume. A rectangular mode represents a real rectangular outline or a deliberately documented bounding-box estimate. For a cup seen along its axis, the outside circular footprint is the starting screen; do not automatically subtract the bore or interior wall area.

Carry CAD measurements into the calculation

For irregular geometry, choose Known/CAD projected area. In CAD, select a plane normal to mold opening, create the silhouette/projection, and measure its area. Keep the drawing revision and projection direction with the result. This tool does not inspect or upload CAD files.

Avoid counting a cavity or runner twice

One-cavity CAD area is multiplied by the identical-cavity count. If a verified area already sums different cavity projections, use Known/CAD mode with cavities = 1. Keep the feed-system area separate. If the input already includes the whole shot including runners, use cavities = 1 and feed-system area = 0. Do not enter runner volume here; the input is a projected area.

Interpretation, assumptions, and limitations

Rectangle and circle are geometric screens, not a CAD or pressure analysis. Complex cores, openings, side actions, stack molds, different cavity pressures, or an uncertain parting plane require a qualified mold/pressure review. No hole-subtraction rule or universal pressure/tonnage factor is assumed. Use the total with a documented cavity-pressure basis; area alone cannot select a machine.

FAQ

Which total goes into Clamp Tonnage?

The current Clamp Tonnage Calculator takes in². Use this tool's total in square inches, including the feed system, and document the cavity-pressure estimate. The cm² total describes exactly the same physical area.

Can I use different cavity shapes?

Obtain each cavity's verified projection and sum them first. Enter that sum in Known/CAD mode with cavities = 1, then add the complete feed-system area once. The identical-cavity multiplier is not a family-mold layout model.