What the ASVAB is actually testing
ASVAB geometry stays strictly at the level of basic 2D shapes (rectangles, triangles, circles, trapezoids) and two 3D shapes (rectangular prisms and cylinders). The test gives you a shape, provides some measurements, and asks for area, perimeter, or volume. There are no proofs, no coordinate geometry beyond plugging into slope-intercept, and no trigonometry.
The skill the test is measuring is formula recall plus careful reading of what measurement is requested.
Area vs. perimeter: don't mix them up
Perimeter is a length — the distance you'd walk around the edge. It's measured in units (feet, meters).
Area is a surface — the space inside. It's measured in square units (ft², m²).
Volume is a space — how much fits inside a 3D shape. Measured in cubic units (ft³, m³).
The test writes questions that make "perimeter" and "area" easy to swap accidentally. Underline the word being asked for before you calculate.
The radius rule for circles
Every circle formula uses radius (r), not diameter (d). If the problem gives diameter, halve it first. This step is easy to skip when you're moving fast, and it costs a full question.
When the height is not an obvious side
For triangles and trapezoids, "height" is the perpendicular distance between base and apex — it's not necessarily one of the sides. The ASVAB occasionally labels a diagram where the height has to be read carefully from the figure rather than assumed.
Connection to other topics
Geometry on the ASVAB frequently embeds algebra: "the perimeter is 40 and the length is twice the width — find the width." That's a geometry formula combined with a linear equation. Recognize the combo and solve in two steps.