ASVAB General Science Study Guide
Updated July 2026 · AFQT · 7 min read
General Science (GS) is the ASVAB subtest that measures your grasp of everyday science across biology, the human body, earth and space science, chemistry, and physics at about a high-school level. It is not one of the four AFQT subtests that decide if you can enlist, but a strong GS score raises several line scores (composites) that open technical and medical jobs. Because the material is wide but shallow, the winning strategy is broad, steady review of key terms and concepts rather than deep study of any one topic. This guide breaks GS down subject by subject and gives you proven test-day strategies.
What General Science Tests and Why It Matters
The ASVAB has nine subtests, and GS is the one that samples general knowledge from the sciences you likely saw in middle and high school. On the CAT-ASVAB you will see about 16 GS questions; on the paper test, 25. You will not do long calculations here, most items are quick recall or simple reasoning.
GS does not count toward your AFQT, so it will not change whether you qualify to enlist. What it does affect is your line scores. Many branches fold GS into composites for electronics, mechanical, and healthcare fields, so a good score can be the difference between qualifying for a job and missing it. See the ASVAB line score calculator to understand which composites use GS.
Core Topics at a Glance
| Area | What to know | Example concepts |
|---|---|---|
| Life science | Cells, genetics, ecology | Cell parts, DNA, food chains |
| Human body | Organ systems and their jobs | Circulatory, respiratory, skeletal |
| Earth science | Geology and weather | Rock cycle, layers of Earth, fronts |
| Space science | The solar system | Planets, moon phases, stars |
| Chemistry | Matter and reactions | Atoms, periodic table, pH |
| Physics | Motion, energy, forces | Newton’s laws, work, energy types |
Biology and Life Science
Start with the cell, the basic unit of life. Know the difference between plant and animal cells, the roles of the nucleus, mitochondria (energy), and ribosomes (protein). Understand photosynthesis (plants make food from sunlight, water, and carbon dioxide) and respiration (cells release energy). Genetics shows up too: DNA carries traits, and dominant genes mask recessive ones. Ecology questions cover food chains, producers and consumers, and how energy flows through an ecosystem.
The Human Body
Expect questions on the major organ systems and what each does. Memorize these pairings:
- Circulatory: heart and blood vessels move blood, oxygen, and nutrients.
- Respiratory: lungs exchange oxygen and carbon dioxide.
- Skeletal: bones support the body and protect organs.
- Muscular: muscles produce movement.
- Nervous: brain, spinal cord, and nerves send signals.
- Digestive: breaks food into usable nutrients.
Knowing which organ belongs to which system answers most human-body items.
Earth and Space Science
Earth science covers the rock cycle (igneous, sedimentary, metamorphic), Earth’s layers (crust, mantle, core), plate tectonics, and weather basics like cold and warm fronts. For space, learn the order of the planets, that the Sun is a star, the cause of moon phases, and why we have seasons. A quick memory hook: My Very Educated Mother Just Served Us Nachos gives you Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
Chemistry Basics
Focus on the structure of the atom: protons (positive), neutrons (neutral), and electrons (negative). Know that the periodic table organizes elements by atomic number, and understand the states of matter and phase changes (melting, freezing, evaporation). The pH scale runs 0 to 14, with acids below 7 and bases above 7.
Example: Which particle carries a negative charge? An electron, which orbits the nucleus.
Physics Basics
Physics on the GS is conceptual, not heavy math. Learn Newton’s three laws of motion, the difference between speed and velocity, and forms of energy (kinetic for motion, potential for stored). Know simple relationships like work = force x distance and the basics of gravity, magnetism, and how electricity flows in a circuit.
Example: A ball held at the top of a hill has potential energy; once it rolls, that becomes kinetic energy.
Top Strategies to Raise Your GS Score
- Use flashcards. Terms, formulas, and body systems are perfect for spaced repetition, so drill them with ASVAB flashcards until recall is instant.
- Learn roots and prefixes. Word parts like bio- (life), geo- (earth), and photo- (light) let you decode unfamiliar terms.
- Read the whole question. Watch for words like not or except that flip what the correct answer should be.
- Eliminate to guess smart. Cross out choices you know are wrong, then pick from what remains, there is no penalty for guessing.
- Move quickly. GS rewards fast recall, so do not linger, mark your best answer and move on.
- Review broadly, not deeply. Since the topics are wide, a little study across every area beats mastering one subject.
How to Practice
The fastest way to build a strong GS score is timed practice plus targeted review. Take the General Science practice test to find your weakest areas, then read the explanation for every question, even the ones you got right. Pair that with the full ASVAB study guide to plan the rest of your prep across all nine subtests. Broad, consistent review of these science basics is the surest way to lift your line scores and qualify for the job you want.
