STANDARDS

CCSS: 6.RP.A.3.C, 7.RP.A.3, MP1, MP3

TEKS: 6.5B, 7.4D

The Science of Supermoons

This special moon will light up the night sky the next two months. Find out when and why!

December 2025/January 2026

By Stephen Zorio

NASA/JPL/USGS

Every year, the moon drifts about 1.5 inches farther from Earth.

Your science textbook says the moon is 238,900 miles from Earth. But that’s just an average! The moon’s distance is constantly changing as it orbits Earth every 27 days. If you were looking at the night sky on October 5, November 7, or December 4 this year, you saw a much closer moon—also known as a supermoon.

Supermoon is not an official scientific term. But it does have a scientific explanation. First, supermoons are a type of full moon. That’s when the moon’s monthly orbit places it on the opposite side of Earth from the sun and it’s fully illuminated. This happens 12 to 13 times each year. Secondly, the moon is near its perigee, which is when the moon is closest to Earth. (The opposite is called an apogee—the moon’s farthest distance from Earth.) A supermoon is any full moon that occurs when the moon is at, or very close to, its perigee.

Your science textbook says the moon is 238,900 miles from Earth. But that isn’t always true! That number is an average. In fact, the moon’s distance is constantly changing. It gets closer and farther away as it orbits Earth every 27 days. If you looked at the night sky on October 5, November 7, or December 4 this year, you saw the moon much closer than usual. That’s known as a supermoon.

Supermoon is not an official scientific term. But it does have a scientific explanation. Firstly, supermoons are a type of full moon. That’s when the moon is on the opposite side of Earth from the sun lights up. This happens 12 to 13 times each year. Secondly, the moon is near its perigee. That’s when the moon is closest to Earth. (The opposite is an apogee—when the moon is farthest from Earth.) A supermoon is a full moon that happens when the moon is around its perigee.

What You Need to Know About the Moon

Watch this video about the moon.

Despite the name, humans generally cannot easily spot the difference in apparent size between a regular full moon and a supermoon. The same goes for the difference between a moon at perigee or apogee. A moon at its closest only appears about 14% larger than at its farthest point. That’s about the difference in size between a quarter and a nickel: You can spot the difference in your hand, but not from thousands of miles away.

Although the rising full moon looks giant in the picture below, that’s actually an optical illusion! Our brain tricks us into thinking the moon is closer when it’s low in the sky.

The name supermoon makes it sound enormous. But a supermoon doesn’t look that much bigger than a normal moon to the human eye. The same goes for the moon at perigee or apogee. At its closest, the moon looks only about 14% larger than when it’s farthest away. That’s about the difference in size between a quarter and a nickel. You could spot the difference if they were in your hand—but not from thousands of miles away!

The rising full moon does look giant in the picture below. But that’s actually an optical illusion. Our brain tricks us into thinking the moon is closer when it’s low in the sky.

How Far is the Moon?

For more than 50 years, an experiment measuring the distance from Earth to the moon has been running.

NASA

1. From 1969 through 1973, U.S. astronauts and robot probes from the Soviet Union left small mirrored reflectors on the moon.

ZUMA Press, Inc./Alamy Stock Photo

2. An observatory shoots a laser beam at a reflector. It takes about 2.5 seconds for the laser beam’s light to return from the moon.

3. Astronomers measure how long the light takes to arrive at the reflector and bounce back to Earth. They use that to calculate the distance to the moon.

How Far is the Moon?

For more than 50 years, an experiment measuring the distance from Earth to the moon has been running.

NASA

1. From 1969 through 1973, U.S. astronauts and robot probes from the Soviet Union left small mirrored reflectors on the moon.

ZUMA Press, Inc./Alamy Stock Photo

2. An observatory shoots a laser beam at a reflector. It takes about 2.5 seconds for the laser beam’s light to return from the moon.

3. Astronomers measure how long the light takes to arrive at the reflector and bounce back to Earth. They use that to calculate the distance to the moon.

However, you may be able to spot a difference in brightness during a supermoon. They appear about 30% brighter than apogee moons—which are sometimes called micromoons. In the coming months, you can test this for yourself: The first supermoon of 2026 is January 4, while the next apogee full moon is May 1. Will you see a difference?

You may be able to spot one difference during a supermoon: brightness. A supermoon looks about 30% brighter than an apogee moon. In the coming months, you can test this for yourself! The first supermoon of 2026 is January 4. The next apogee full moon is May 1. Will you see a difference?

Percent of a Number

Watch a math video about finding the percent of a number.

FINDING PERCENT OF A NUMBER

A percent is a ratio out of 100. When you know a whole and a percent that represents part of that whole, you can multiply them together to find the exact value that the percent represents.

EXAMPLE

On average, the moon is 238,900 miles from Earth. The average distance of a perigee moon is 94.52% of that. How many miles away is a perigee moon on average?

STEP 1

Convert the percent to a decimal by dropping the % sign and dividing by 100.

94.52% = 94.52 ÷ 100 = 0.9452

STEP 2

Multiply the decimal by the whole.

0.9452 × 238,900 = 225,808.28

STEP 3

Round your answer to the nearest whole number if necessary.

225,808.28 = 225,808

So a perigee moon is about 225,808 miles from Earth on average.

FINDING PERCENT OF A NUMBER

A percent is a ratio out of 100. When you know a whole and a percent that represents part of that whole, you can multiply them together to find the exact value that the percent represents.

EXAMPLE

On average, the moon is 238,900 miles from Earth. The average distance of a perigee moon is 94.52% of that. How many miles away is a perigee moon on average?

STEP 1

Convert the percent to a decimal by dropping the % sign and dividing by 100.

94.52% = 94.52 ÷ 100 = 0.9452

STEP 2

Multiply the decimal by the whole.

0.9452 × 238,900 = 225,808.28

STEP 3

Round your answer to the nearest whole number if necessary.

225,808.28 = 225,808

So a perigee moon is about 225,808 miles from Earth on average.

Find percents related to the moon. Round answers to the nearest whole number. Record your work and answers on our answer sheet.

In 2026, there will be 13 full moons—23% will be supermoons. How many is that?

A. A perigee moon is 225,803 miles from Earth. A supermoon’s distance is 90% of perigee or higher. How far away is that?

B. The closest supermoon since 1948 was on November 14, 2016 (shown at left). It was 98.105% of perigee. How far away was that supermoon?

July 10 was the farthest full moon of 2025, at 243,520 miles from Earth. The supermoon on April 27 was about 91.1% of that distance. How far away was it?

On November 5, the moon was about 221,817 miles from Earth. It was the closest supermoon of 2025. An apogee moon—when the moon is at its farthest—is about 113.6% of that. What’s the average distance of an apogee moon rounded to the nearest thousand?