Basketball Hoop Size
A regulation basketball rim is 18 inches across on the inside, mounted 10 feet above the floor, 6 inches out from a backboard 72 inches wide. This interactive page draws regulation and home-hoop backboards to scale, shows how much space a ball has inside the rim for every ball size, and helps you check the height of your own hoop.
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Quick answer
A regulation basketball hoop has a 9-inch radius, because the inside rim diameter is 18 inches. NBA, NCAA and high-school rims are 10 feet high, measured from the court to the top of the rim. The 6-inch backboard measurement means from the front face of the backboard to the nearest inside edge of the ring.
Basketball hoop size explorer
Basketball Court and Hoop Pack
Printable dimensioned backboard and rim diagrams (NBA/NCAA and FIBA), a half-court diagram for drills, a shooting practice log and a hoop height and ball size chart.
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- Install checklist (PDF/DOCX)
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Printable Basketball Hoop Install ChecklistKey basketball hoop measurements
Use these standard dimensions for regulation hoops and common backboard references.
| Measurement | US value | Metric value | Notes |
|---|---|---|---|
| Hoop radius | 9 in | 22.9 cm | Inside radius |
| Hoop diameter | 18 in | 45.7 cm | Inside diameter |
| NBA rim height | 10 ft | 3.05 m | Court to top of rim |
| Backboard size | 72 × 42 in | 183 × 107 cm | NBA/NCAA/HS regulation |
| FIBA backboard | 70.9 × 41.3 in | 1.80 × 1.05 m | International |
| Backboard to ring | 6 in | 15 cm | Face to nearest inside edge |
| Rim center offset | About 15 in | About 38 cm | From backboard face |
| Front inside edge | About 24 in | About 61 cm | From backboard face |
Regulation hoop dimensions
| Measurement | NBA / NCAA / US high school | FIBA (international) |
|---|---|---|
| Rim height (top of rim) | 10 ft | 3.05 m |
| Rim inside diameter | 18 in | 45 cm (45–45.9 cm) |
| Rim to backboard | 6 in | 15 cm |
| Backboard size | 72 × 42 in | 1.80 × 1.05 m |
| Inner rectangle (shooter’s square) | 24 × 18 in | 59 × 45 cm |
| Backboard border lines | 2 in | 5 cm |
| Net length | 15–18 in | 40–45 cm |
The top of the rim sits level with the bottom edge of the inner rectangle painted on the backboard. Some US high-school courts still use older, smaller backboards, which rule books allow in certain cases; check your state association.
How much room does the ball have?
| Ball | Circumference | Diameter | Space each side in an 18 in rim | Typical players |
|---|---|---|---|---|
| Size 7 | 29.5 in | 9.39 in | 4.3 in | Men and boys about 15+ |
| Size 6 | 28.5 in | 9.07 in | 4.5 in | Women and girls; boys about 12–14 |
| Size 5 | 27.5 in | 8.75 in | 4.6 in | Youth about 9–11 |
| Size 4 | 25.5 in | 8.12 in | 4.9 in | Young children about 5–8 |
| Size 3 | 22 in | 7.00 in | 5.5 in | Mini balls |
A men’s ball is just over half the width of the rim — two balls side by side almost fit. That’s why shots that arrive at a steeper angle have a bigger target: seen from above, the opening looks larger the more steeply the ball drops. Age ranges vary by league; check yours.
Using the hoop explorer
- Choose a backboard: regulation, FIBA or a common home or portable size.
- Pick a ball size to see its diameter and the clearance inside the rim.
- Switch between inches and centimetres.
- Enter the height you measured from the floor to the top of your rim to see how far it is from 10 feet.
How to measure your hoop height
- Measure from the playing surface straight up to the top edge of the front of the rim — not to the backboard or the net hooks.
- Use a tape measure and a helper, or a long pole marked at 10 ft.
- Measure at the front of the rim; if the hoop is not level, measure at both sides.
- Adjustable portable hoops often show heights on a scale, but check them — the scale can be out by an inch or more.
- Regulation is 120 inches; many players are surprised how far off home hoops are.
Rim heights for younger players
Many youth programmes lower the rim for young children so they can shoot with good technique instead of heaving the ball, commonly using 8 or 9 feet for younger age groups and moving to 10 feet around the start of secondary school. Mini-basketball under FIBA rules uses a rim height of 2.60 m (about 8 ft 6 in) with a smaller ball. Rules differ between leagues and countries, so check your organisation’s guidelines.
Choosing a home hoop
| Backboard width | Type | Suits |
|---|---|---|
| 44 in | Portable, plastic or polycarbonate | Young children, casual shooting |
| 48–50 in | Portable, polycarbonate or acrylic | Family driveways |
| 54 in | Portable or in-ground, acrylic or glass | Teens, regular play |
| 60 in | In-ground, tempered glass or acrylic | Serious practice with realistic rebounds |
| 72 in | In-ground, tempered glass | Regulation feel; needs a large driveway or court |
A bigger, stiffer backboard and a solid in-ground pole give truer bank shots and less wobble. The rim itself is 18 inches on almost every hoop, even small ones.
Worked example
A size 7 ball has a circumference of 29.5 inches, so its diameter is 29.5 ÷ π ≈ 9.39 inches. In an 18-inch rim that leaves (18 − 9.39) ÷ 2 ≈ 4.3 inches of space on each side if the ball goes exactly through the middle, and 18 ÷ 9.39 ≈ 1.92 balls would fit across the rim.
Why the rim is 10 feet high
When James Naismith invented basketball in 1891, he nailed peach baskets to the balcony rail of a gymnasium in Springfield, Massachusetts. The rail happened to be 10 feet above the floor, and the height has stayed the same ever since, even as players have grown taller. Backboards were added a few years later, partly to stop spectators in the balcony from interfering with shots.
Court markings near the hoop
- The free-throw line is 15 ft from the front of the backboard in NBA, NCAA and US high school basketball.
- FIBA and the NBA use a no-charge semicircle in front of the basket (FIBA: 1.25 m radius; NBA: 4 ft).
- The three-point line is at different distances in the NBA, NCAA and FIBA — check the rule book for your level.
AI-assisted content
Explanations were drafted with AI assistance and reviewed before publishing against published NBA, NCAA and FIBA dimensions.
Frequently asked questions
What is the radius of a basketball hoop?
A regulation basketball hoop radius is 9 inches, measured inside the rim. That comes from the standard 18-inch inside diameter.
How high is an NBA basketball hoop?
An NBA hoop is 10 feet high, measured from the playing surface to the top of the rim. That is the same regulation height used in NCAA and most high-school basketball.
What is the size of the basketball board?
A regulation NBA, NCAA and high-school backboard is 72 inches wide by 42 inches tall. FIBA backboards are 1.80 m by 1.05 m, which is very close but not identical.
What is the diameter of a basketball hoop?
18 inches (45.7 cm) inside the rim.
How high is a basketball hoop?
10 feet (3.05 m) from the floor to the top of the rim.
How big is a regulation backboard?
72 × 42 inches in the NBA and NCAA; 1.80 × 1.05 m under FIBA rules.
How far is the rim from the backboard?
6 inches (15 cm).
How many basketballs fit in a hoop?
Almost two size 7 balls side by side.
What size is the square on the backboard?
24 × 18 inches.
Is a FIBA hoop the same as an NBA hoop?
Almost: both are 10 ft (3.05 m) high with an 18 in (45 cm) rim; FIBA backboards are 1.80 × 1.05 m.