Math Education

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Area of a Circle Formula: How to Calculate & Examples

Published: 11.07.2026·Updated: 22.07.2026

Dewi Lestari

Mathematics Specialist

Area of a Circle Formula: How to Calculate & Examples

The area of a circle formula is A = π × r² (πr²), where r is the radius and π ≈ 22/7 or 3.14. If you know the diameter (d), use A = ¼ × π × d². Quick example: a circle with a radius of 7 cm has an area of (22/7) × 7² = 154 cm².

The area of a circle is the region inside its circumference; r is the radius.

How to Calculate the Area of a Circle + Worked Example

The area of a circle is the size of the region inside its circumference. The main formula uses the radius:

If you know the diameter, convert it to the radius first (r = d/2) or use A = ¼πd² directly.

Worked example: A circular garden has a diameter of 28 m. What is its area? (π = 22/7)

Step 1: d = 28 m → r = 14 m. Step 2: r² = 196. Step 3: A = (22/7) × 196 = 22 × 28 = 616 m².

So the area of the garden is 616 m².

Why It Matters

The area of a circle formula is introduced in Grade 6 and deepened in Grade 8. It is one of the most frequently used formulas in mathematics and is the foundation for the surface areas of cylinders, cones, and spheres. In real life it is used to work out the area of round pools, pizzas, wheels, and signal coverage.

See also: Circumference of a Circle, Surface Area of a Cylinder, and Surface Area of a Sphere. Browse everything at Algonova Mathematics.

Want your child to master maths with an experienced mentor? Try a free Master Class at Algonova.

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Does Algonova teach mathematics for primary, junior high, and senior high kids?

Yes, Algonova Indonesia offers a complete math program for kids aged 6 to 17, covering all school levels from primary, junior high, to senior high. Each level has a dedicated curriculum aligned with the child's cognitive stage and the Indonesian school curriculum (Kurikulum Merdeka). For primary school (6-12): basic operations, fractions, simple geometry, and introduction to algebra. For junior and senior high (13-17): algebra, quadratic equations, basic trigonometry, advanced geometry, basic calculus, statistics, UTBK SNBT preparation, and advanced topics. All classes are online live with certified teachers in small groups of up to 10 students per class. Our method is built on visual conceptual understanding, not formula memorisation. Try a free trial class for a child's level diagnostic and recommended learning path.

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Yes. For mathematics Algonova Indonesia offers a free 45 minute diagnostic session with no commitment. The format is called Metode Diagnostik Algonova. No credit card is needed and there is no auto subscription afterwards. Note that these 45 minutes are a diagnostic session, not a regular class. A regular math class runs 90 minutes, while the coding and design tracks have their own introductory format, a free 60 minute master class. During the diagnostic a certified teacher maps the child's level: which topics are already solid and where the gaps sit. The child also tries the online learning platform and works through first problems matched to their school level. After the session parents receive a personal learning plan based on the diagnostic result, plus a transparent explanation of program, schedule, and pricing from Rp 102,000 per lesson. To book, fill in the form on the website.

How many students are in one Algonova math class?

Algonova Indonesia math classes come in three formats: 1-on-1 private, a mini-group of 2–4 kids, and a group of up to 10 students with similar ability and school grade levels. This small group format is deliberately chosen because it provides the optimal balance between social interaction with peers and personal teacher attention. In a mini-group, every child averages about 10 minutes of direct teacher interaction in a single session. Compare with traditional offline bimbel typically of 20-40 students per class — direct interaction there is only 1-2 minutes per child, or none at all. For families wanting full attention, one-on-one private class format is also available with one student per teacher. This format is more intensive and suits competition preparation, catching up from severe gaps, or specific topic depth.

How much does kids math tutoring at Algonova Indonesia cost?

Kids math tutoring at Algonova Indonesia starts from Rp 102,000 per lesson. The price includes a live session with a certified teacher, digital learning materials, online platform access, and an official certificate upon completing each program level. The transparent 'starting from' rate is the same across all school levels — the final quote depends only on class format (private, mini-group, or group) and how many sessions per week you choose. Groups are the most affordable option; private classes are more intensive and suit competition prep or closing larger gaps. Full pricing details are shared transparently after the free trial class. No surprise fees — every cost component is explained before formal enrolment. To receive the latest pricing details, fill in the booking form on the website.

Is math tutoring fully available online?

Yes, all Algonova Indonesia math programs are fully available online with live sessions taught by certified teachers — not recorded videos. Kids learn in real time in small groups of up to 10 students, with two-way interaction, live Q&A, and problems worked on alongside the teacher throughout the class. To join online class, a child only needs a computer or laptop with a camera, a stable internet connection, and a headset. The Algonova platform runs directly in the browser so no special software installation is required. Kids can write problems in a regular notebook or on a tablet with stylus. Because every class is fully online, families can join from anywhere in Indonesia and easily fit lessons around school and other activities.

What makes Algonova math tutoring effective for Indonesian kids?

Three main factors make Algonova math tutoring effective for Indonesian kids. First, the curriculum aligns with Kurikulum Merdeka used in national schools, so what is learned at Algonova directly helps with school lessons and exams. Second, the methodology is built on visual conceptual understanding (not formula memorisation). Kids learn to break big problems into small systematic steps — a thinking pattern transferable to other subjects like science and IT. Third, small groups of up to 10 students per class let teachers adjust pace to each child's ability. Slower kids get personal help, while faster kids don't get bored waiting. The result: most Algonova students see math grade improvements at school within the first 2-3 months.

What if my child is behind from earlier math grades?

Algonova Indonesia is specifically designed to help kids behind catch up in a way that doesn't make them feel defeated or ashamed. Every new student starts with a free diagnostic during the trial class to identify exactly where the gap occurred. Based on the diagnostic, the teacher builds a personal learning path that closes the gap from the most basic foundation. For example, a junior high student weak in algebra might actually be behind in primary school fraction operations. We go back to the foundation, then progress gradually without comparison with other peers. Many Algonova students who initially started 1-2 grade levels behind successfully caught up and even surpassed classmates within 3-6 months with weekly classes and consistent homework. It's never too late to start. Try a free trial class for diagnosis without commitment.

What is the formula for the area of a circle?

The area of a circle is A = πr², where r is the radius. If you know the diameter, use A = ¼πd². The value of π ≈ 22/7 or 3.14.

What is the difference between area and circumference of a circle?

The area of a circle = πr² and measures the region inside (units cm²). The circumference = 2πr or πd and measures the length of the edge (units cm).

How do you find the area of a circle when you only know the diameter?

Divide the diameter by two to get the radius (r = d/2), then use πr². Or use A = ¼πd² directly. Example: d=28 → r=14 → (22/7)×196 = 616.

In which grade is the area of a circle taught?

The area of a circle is introduced in Grade 6 and deepened in Grade 8 within the chapter on circles.

What Grade Is Area of a Circle Taught In?

The area of a circle is introduced in Grade 6 and deepened in Grade 8 of SMP (junior secondary school) in the Circle chapter, after pupils have met the circumference of a circle. The formula is A = πr², with π ≈ 22/7 or 3.14. This concept is the foundation for the surface area of the cylinder, the cone, and the sphere in Grade 9.

The most common mistake is using the diameter directly without halving it to get the radius. Try a free Algonova class to gauge your child's grasp of geometry, or explore the Algonova math program. See also Circumference of a Circle and Area of a Rectangle Formula.

Other Shapes & Math Topics

Want your child to learn maths with an experienced mentor? Try a free Master Class at Algonova — a 60-minute session for a level assessment, at no cost.

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