What Is the Name of a 7 Sided Shape? | The Term Teachers Expect

A 7-sided polygon is a heptagon, with seven edges and seven corner points.

If you searched “What Is the Name of a 7 Sided Shape?”, you’re usually after one clean word you can use on homework, a quiz, or a label on a diagram. That word is heptagon. It’s the standard term in geometry, and it’s the one most textbooks use.

Still, seven sides can trip people up. You might hear “septagon,” you might wonder if a curved coin counts, or you might be unsure when a shape stops being “regular.” This article clears that up with plain definitions, simple formulas, and a few ways to spot seven sides without counting twice.

Name For a Seven-Sided Shape In Geometry

Heptagon is the usual name for a seven-sided polygon. The prefix hepta- comes from Greek for “seven,” and -gon points to angles or corners. A heptagon has:

• 7 sides (straight line segments)
• 7 vertices (corner points)
• 7 interior angles (one at each vertex)

You’ll also see 7-gon as shorthand. It means the same thing, just in a compact label on worksheets and diagrams.

Heptagon Vs. Septagon

Some sources use septagon as a second name for a seven-sided polygon. In school settings, heptagon is safer since it matches the Greek prefix pattern used in many polygon names. If a teacher or textbook uses “heptagon,” stick with that term in your work.

What Counts As a “7 Sided Shape”

In geometry class, “7 sided shape” usually means a polygon, so the sides are straight. A coin with seven rounded edges can look seven-sided, yet its boundary is curved. Designers still call those “heptagonal” in casual talk, though in strict geometry it’s not a polygon unless each side is a straight segment.

Parts Of a Heptagon

Once you know the name, the next step is knowing what you’re pointing at on a diagram. These terms come up a lot in lessons and test questions.

Sides, Vertices, And Angles

A heptagon’s sides meet in pairs. Each meeting point is a vertex. Each vertex creates an interior angle inside the shape.

Diagonals

A diagonal connects two non-adjacent vertices. In a heptagon, each vertex connects by diagonals to 4 other vertices (not itself, not its two neighbors). That counts each diagonal twice, so the total number of diagonals is:

(7 × 4) ÷ 2 = 14 diagonals

Perimeter

The perimeter is the distance around the outside. Add all 7 side lengths. If the heptagon is regular and each side is length s, then perimeter P = 7s.

Regular And Irregular Heptagons

The word “regular” has a tight meaning in geometry. It’s not about being neat or drawn with a ruler. It’s about equality.

Regular Heptagon

A regular heptagon has:

• All 7 sides the same length
• All 7 interior angles the same size

It has rotational symmetry (you can rotate it and it matches itself) and reflection symmetry (you can flip it across certain lines and it matches itself).

Irregular Heptagon

An irregular heptagon still has seven sides, yet the side lengths, angles, or both are not all equal. Many hand-drawn seven-sided shapes are irregular, and that’s fine—“heptagon” still fits as long as it’s a closed figure made of seven straight segments.

Convex And Concave

Heptagons come in two main “bend” styles:

• Convex: all interior angles are less than 180°, and no vertex caves inward.
• Concave: at least one interior angle is greater than 180°, creating an inward dent.

A concave heptagon still has seven sides. The dent changes diagonals and angle layouts, yet the name stays the same.

Angle Facts That Make Seven Sides Easier

If you’re learning polygons, angles are where the points add up fast. The good news: the formulas are short, and once you learn them, you can check your work in seconds.

Sum Of Interior Angles

For any simple polygon with n sides, the sum of interior angles is:

(n − 2) × 180°

For a heptagon, n = 7:

(7 − 2) × 180° = 900°

So, every heptagon—regular or irregular—has interior angles that add up to 900°, as long as it’s a simple polygon (no self-crossing sides).

Each Interior Angle In a Regular Heptagon

In a regular heptagon, the 900° total is split evenly across 7 equal angles:

900° ÷ 7 = 128 4/7°

As a decimal, that’s about 128.57° per interior angle.

Exterior Angles

An exterior angle is the “turn” you make when you walk around the polygon, extending one side and turning to follow the next. For any convex polygon, the exterior angles add to 360°.

In a regular heptagon, each exterior angle is:

360° ÷ 7 = 51 3/7° (about 51.43°)

How To Tell If a Shape Has Seven Sides

Counting sides sounds simple until you’re staring at a messy sketch, a logo, or a tilted photo. Here are a few checks that keep you from double-counting a corner or skipping a tiny edge.

Use The Vertex Count

Each side ends at a vertex. So if you can mark the corner points cleanly, count vertices first. Seven vertices means seven sides for a simple polygon.

Trace With a Finger Or Pencil

Start at one vertex and trace the boundary in one direction. Say the vertex names out loud as you go: A, B, C, D, E, F, G, then back to A. If you return to the start after seven moves, you’ve got seven sides.

Watch For Split Edges

Some drawings add a point on the middle of a side, making it look like a corner when it isn’t. A true vertex changes direction. If the line stays straight, that point is not a vertex.

Heptagon Facts And Formulas In One Place

This is the “one glance” section many students want: definitions, counts, and formulas grouped in a single view. For word problems, it’s handy as a check list.

Two reliable references for definitions and standard terminology are the Britannica Dictionary entry for “heptagon” and the Wolfram MathWorld page on heptagons. You can read them here: Britannica Dictionary definition of heptagon and Wolfram MathWorld entry on heptagons.

Heptagon Detail	Value Or Rule	Notes
Number of sides	7	Straight segments for a polygon
Number of vertices	7	Corner points where sides meet
Number of interior angles	7	One at each vertex
Sum of interior angles	900°	(7 − 2) × 180°
Each interior angle (regular)	900° ÷ 7	128 4/7° (about 128.57°)
Each exterior angle (regular, convex)	360° ÷ 7	51 3/7° (about 51.43°)
Number of diagonals	14	(7 × 4) ÷ 2
Perimeter (regular)	P = 7s	s is side length
Area (regular)	A = (7/4)s²·cot(π/7)	Uses trig; s is side length
Area (regular, with apothem)	A = (P × a)/2	a is apothem, P is perimeter

Regular Heptagon Geometry You’ll See In Class

Most classroom questions lean on the regular heptagon, since equal sides and equal angles make algebra cleaner. If you’re solving for side length, perimeter, or area, these are the pieces that show up again and again.

Radius, Apothem, And Center

If a regular heptagon is drawn inside a circle, each vertex sits on the circle, and the center of the circle is the center of the heptagon. Two common lengths come from that setup:

• Radius: the distance from the center to a vertex.
• Apothem: the distance from the center to the midpoint of a side, meeting the side at 90°.

The apothem is a handy bridge between perimeter and area, since the area can be found from A = (P × a)/2.

Central Angles

Draw segments from the center to each vertex. You get 7 congruent triangles. Each central angle is a full turn split into 7 equal parts:

360° ÷ 7 = 51 3/7°

That number matches the exterior angle of a regular heptagon, which is a neat connection students often spot after a couple of exercises.

Why The Regular Heptagon Feels “Odd”

Some regular polygons show up in basic construction lessons with only a straightedge and compass. A regular heptagon does not fall into the simplest set of those classic constructions, so many school courses mention it less than triangles, squares, pentagons, and hexagons. You can still draw a clean regular heptagon with a protractor, a ruler, or a digital tool, and the angle facts above still hold.

Ways Seven-Sided Shapes Show Up In Design

Heptagons pop up in pattern work, logos, and decorative trims, mainly because seven has a distinctive rhythm. You won’t see perfect regular heptagons as often as hexagons, yet you’ll meet “heptagon-like” outlines in everyday objects.

When you spot one, use the same rule: if it’s a closed outline with seven straight edges, it’s a heptagon. If the edges curve, it can still look heptagonal, yet it’s not a polygon in the strict sense.

Where You Might See Seven Sides	What To Check	Common Mix-Up
Logo badges and emblems	Count corner turns, not tiny line breaks	Extra points on a straight edge
Decorative tiles	Look for seven straight borders	Curved borders that only look straight
Architectural floor plans	Mark the vertices on the outer wall line	Indented bays that create concave corners
Game tokens or icons	Rotate the shape; count the edges as they face you	Shadow lines mistaken for edges
Coin outlines with “seven bumps”	Check if edges are straight segments	Rounded edges called “heptagonal” casually
Craft templates	Trace and label vertices A–G	Overlapping lines that cross inside
Charts with seven categories	Check if it’s a 7-point star or a 7-sided frame	Heptagram (star) confused with heptagon

Common Mix-Ups And How To Fix Them

Most mistakes come from mixing up sides, angles, and “points” on a star shape. A short reset can save you points on a test.

Heptagon Vs. Heptagram

A heptagon is a seven-sided polygon. A heptagram is a seven-point star. A heptagram can be drawn inside a regular heptagon, yet the star’s boundary crosses itself, so it’s not the same shape.

Seven Sides Vs. Seven Angles

For a simple polygon, sides and interior angles match in count. If you count seven angles, you’ve counted seven vertices. That means seven sides too.

Self-Crossing Shapes

If the outline crosses itself, some formulas change. The interior-angle-sum rule of 900° is for simple polygons where the boundary does not intersect itself. When in doubt, redraw the shape as a clean outline first.

Mini Checklist For Homework And Quizzes

• Use the term heptagon for a seven-sided polygon.
• Confirm it’s a polygon: seven straight edges, closed outline.
• Interior angles add to 900° for any simple heptagon.
• Regular heptagon interior angle is 900° ÷ 7 (about 128.57°).
• Regular heptagon exterior angle is 360° ÷ 7 (about 51.43°).
• Diagonals in a heptagon: 14.
• If the outline is a star, it’s a heptagram, not a heptagon.