Elon Musk's aerospace company, SpaceX, is building a gigantic rocketship to reach Mars.

The Big Falcon Rocket, or BFR, will use a fully reusable booster and a fully reusable spaceship.

In SpaceX's "final' design, the two-part launch system stands about 387 feet tall and 30 feet in diameter.

We created a interactive size comparison tool to show how big a real-life BFR might be.

Elon Musk's rocket company, SpaceX, is working on something big — really big.

The Big Falcon Rocket, or BFR, is an unprecedented launch system designed to rocket up to 100 people and 150 tons of food, water, and other supplies to the surface of Mars. The end goal: colonize the red planet and back up the human race.

Musk revealed what he described as the final BFR design in September. It's made of two giant stages: a fully reusable rocket booster on the bottom, and a fully reusable spaceship on top. The first crewed mission is penciled in for 2023 and is expected to blast a Japanese billionaire and a group of artists around the moon.

The illustration below shows the approximate length and shape of each part of the BFR system.

The BFR's dimensions and presumed capabilities are impressive — so much so that quite a few people in the aerospace industry are puzzled by how it will be done. They also wonder if it can be built successfully by a private company on a budget of about $2-10 billion. That's Musk's latest estimate for how much the development of BFR will cost; the sum is actually a relative pittance compared to what NASA is paying for its new (and not reusable) Space Launch System.

To help understand the magnitude of what Musk and his thousands of employees at SpaceX are trying to accomplish, Business Insider created an interactive size-comparison graphic.

Next to the rendering of BFR shown below, you'll see a series of familiar objects at the rocket's base. (Some are so small that you may have to scroll down a bit.) Toggle through the 20 comparisons by clicking "next" or "back" to get a sense of the rocket's scale.