Are there really more stars in the Universe than sand on earth?

We often hear the awe-inspiring statement that there are roughly $X$ stars in the universe. The number most commonly used to complete this statement is $10^{22}$ , which is ten sextillion (a 1 followed by 22 zeros). This number is widely known because it gives a simple, powerful idea of the cosmos’s vastness.

This famous figure is based on a basic scaling model: multiply the estimated number of stars in an average galaxy (about 100 billion) by the estimated number of galaxies (also about 100 billion). The result is $10^{22}$ total stars.

However, this number is scientifically considered the lowest possible estimate. While $10^{22}$ is conventional, modern space data suggests the true count is much higher.

Only What We Can See: The Observable Universe

Any star count is fundamentally limited to the observable universe—the spherical region of space from which light has had time to reach Earth since the Big Bang. Since we can’t see beyond this horizon, any number we calculate is always just a lower bound for the entire universe.

Early surveys missed many faint, smaller galaxies, which naturally kept the star estimates low. The number of galaxies in the universe is the biggest factor in the star count, and that number is constantly being revised upward as technology improves.

Modern Science: A Much Higher Range

Today, astronomers agree the total star count is likely much larger than $10^{22}$ . Instead of 100 billion galaxies, current deep-field surveys suggest there are between 200 billion and 2 trillion galaxies.

Using updated galaxy figures, the estimate rises substantially. If we use a mid-range projection, the total stellar population is closer to $2 \times 10^{23}$ , or 200 sextillion stars. This shows that the current scientific consensus operates within a broad range, from $10^{22}$ to $10^{23}$ . Some highly theoretical calculations suggest even more extreme totals, approaching $4.5 \times 10^{24}$ .

The Challenge of the Cosmic Census

Counting stars across the cosmos is not a simple inventory; it’s a complex process of using statistical modeling and high-tech observation.

The method for estimating stars relies on two main ingredients: the average number of stars per galaxy and the total number of galaxies. Astronomers estimate the stars in a galaxy by measuring its total brightness and then calculating the amount of stellar mass that brightness represents. The assumption of 100 billion stars per galaxy is conservative because it tends to overlook the enormous population of tiny, dim red dwarf stars, which are hard to see but numerous.

Using New Technology to Count More

Finding the total number of galaxies is the toughest challenge. To find galaxies hidden by cosmic dust, astronomers use specialized instruments like the ESA Herschel observatory. This space telescope “counts” galaxies and measures their brightness using infrared light, which can penetrate the dust clouds that block normal visible light. By charting the rate at which stars have formed throughout cosmic history, this infrared census adds confidence to the high-end calculations.

The Universe Changes

Because light takes billions of years to travel, we see distant galaxies as they looked in the past. Since stars are constantly forming and dying, the total number of stars is not static. Calculating the total number of stars existing currently requires accounting for this constant change throughout the universe’s history.

Earth’s Sand: A Comparison That Doesn’t Quite Work

The cosmological statement comparing the number of stars to grains of sand is meant to convey an incomprehensible vastness. However, the comparison relies on a terrestrial estimate that is itself full of guesswork.

To start the calculation, we must define the average size of a sand grain. A typical grain of beach sand measures about half a millimeter across. At that density, about 8,000 grains fit into a single cubic centimeter.

The Guesswork of Beach Volume

The biggest challenge is estimating the total volume of all the beach sand on Earth. This requires three extremely uncertain estimates: 1) the total length of the world’s coastlines; 2) how much of that coastline is sandy beach; and 3) the average depth of the sand on those beaches. Because these estimates are largely educated guesses, the final count has a massive margin of error.

Based on detailed estimates, the consensus centers around a volume that works out to approximately $5 \times 10^{21}$ (5 sextillion) grains of sand. Experts acknowledge that this estimate could easily be off by a factor of 2, meaning the true range could be between $2.5 \times 10^{21}$ and $1 \times 10^{22}$ grains.

The Cliché Assessed: Are Stars Really More Numerous?

When we compare the estimated ranges for stars and sand, a critical overlap emerges:

Comparative Estimates: Stars vs. Sand Grains

Quantity	Low-End Estimate	High-End Estimate
Stars in Observable Universe	$1 \times 10^{22}$ (10 Sextillion)	$2 \times 10^{23}$ (200 Sextillion)
Grains of Sand on Earth’s Beaches	$2.5 \times 10^{21}$ (2.5 Sextillion)	$1 \times 10^{22}$ (10 Sextillion)

Since the low-end estimate for stars is statistically equal to the high-end estimate for sand ( $1 \times 10^{22}$ ), the common claim that there are definitively more stars than sand grains is statistically unprovable. The comparison is best viewed as a powerful, poetic image rather than a rigorous scientific ratio.

The most common number for the stars in the observable universe is $10^{22}$ (10 sextillion), but modern estimates extend as high as $2 \times 10^{23}$ . The comparison between stars and grains of sand is flawed: the scientific ranges for both quantities overlap, meaning the famous claim that there are definitively “more stars than sand” cannot be verified.

Are there really more stars in the Universe than sand on earth?