A good physics constants list does more than give you numbers to memorize. It helps you recognize when a constant belongs in a formula, what its unit is telling you, and why it appears across many topics. This reference hub collects the most common physical constants with units, explains what they mean in plain language, and shows where students usually meet them in mechanics, electricity, waves, thermodynamics, and modern physics. Use it as a physics reference sheet, a revision tool, and a quick check whenever a problem feels abstract.
Overview
This article is a practical physics constants list for students who want more than a table of symbols. You will find the constant, its standard value, its SI unit, and the context in which it usually appears. The aim is not to turn every constant into something to memorize blindly. The aim is to help you connect the constant to the kind of problem you are solving.
In exam prep, students often confuse three separate things: constants, variables, and unit conversions. A constant is a fixed quantity used throughout physics. A variable changes from problem to problem. A conversion factor changes the way you express a quantity but not the underlying physics. Keeping those roles separate makes formulas much easier to read.
Below is a compact list of common constants that appear in high school and introductory university physics. Values are given in familiar SI form, usually rounded to a level that is useful for coursework. In many exams, a formula sheet gives the exact value or an accepted approximation. If your course uses a specific data booklet, treat that booklet as your final authority during revision.
Core physics constants list
- Speed of light, c = 3.00 × 108 m/s
What it means: the speed of electromagnetic waves in vacuum.
Common topics: waves, optics, relativity, photon energy. - Gravitational acceleration near Earth, g = 9.81 m/s2 (often 9.8 or 10 m/s2 in simple problems)
What it means: the acceleration of freely falling objects near Earth’s surface.
Common topics: mechanics, projectile motion, energy, forces. - Universal gravitational constant, G = 6.67 × 10-11 N·m2/kg2
What it means: the constant in Newton’s law of gravitation.
Common topics: planetary motion, gravitation, field strength. - Planck constant, h = 6.63 × 10-34 J·s
What it means: links energy and frequency through E = hf.
Common topics: quantum physics, photons, photoelectric effect. - Elementary charge, e = 1.60 × 10-19 C
What it means: magnitude of the charge carried by a proton, and the magnitude of the electron’s charge.
Common topics: electric charge, electric fields, circuits, particle physics. - Electron mass, me = 9.11 × 10-31 kg
What it means: rest mass of an electron.
Common topics: atomic physics, charge-to-mass questions, modern physics. - Proton mass, mp = 1.67 × 10-27 kg
What it means: rest mass of a proton.
Common topics: nuclear and atomic calculations. - Avogadro constant, NA = 6.02 × 1023 mol-1
What it means: number of particles in one mole.
Common topics: thermal physics, chemistry-linked physics, particle counting. - Boltzmann constant, k = 1.38 × 10-23 J/K
What it means: links temperature to energy at particle level.
Common topics: thermodynamics, kinetic theory. - Gas constant, R = 8.31 J/(mol·K)
What it means: constant in the ideal gas equation pV = nRT.
Common topics: gases, thermal physics. - Permittivity of free space, ε0 = 8.85 × 10-12 F/m
What it means: appears in electric force and field equations in vacuum.
Common topics: electrostatics, capacitance. - Permeability of free space, μ0 = 4π × 10-7 H/m
What it means: appears in magnetic field equations.
Common topics: electromagnetism. - Coulomb constant, ke = 8.99 × 109 N·m2/C2
What it means: the proportionality constant in Coulomb’s law.
Common topics: electric forces and fields. - Stefan–Boltzmann constant, σ = 5.67 × 10-8 W·m-2·K-4
What it means: links temperature to radiated power per unit area.
Common topics: thermal radiation. - Wien displacement constant, b = 2.90 × 10-3 m·K
What it means: links peak wavelength and temperature.
Common topics: blackbody radiation.
You do not need every one of these for every course. GCSE students will meet far fewer than first-year university students. Still, seeing them in one place helps you notice patterns: some constants connect force and field, some connect energy and frequency, and some convert between microscopic and macroscopic descriptions.
Topic map
This section shows where the most common constants appear and why they matter. If you have ever asked, “Why do I keep seeing this symbol?” this is the part to bookmark.
Mechanics and gravitation
The constant most students meet first is g. It appears in equations such as v = u + at, s = ut + 1/2at2, and weight W = mg. Here, g is not a universal constant in every location, but in introductory problems it is treated as a standard value near Earth’s surface. Students often mix up g and G. The lower-case g is gravitational acceleration near Earth. The upper-case G is the universal constant used in Newton’s law of gravitation, F = Gm1m2/r2.
If you are solving motion questions, constants are only one part of the setup. Drawing forces clearly is often what unlocks the problem. For that, see Free Body Diagrams Explained: Rules, Examples, and Common Mistakes. If your problem includes trajectories, pair this hub with Projectile Motion Problems: Horizontal and Angled Launch Questions Solved.
Waves, light, and optics
The speed of light value, c = 3.00 × 108 m/s, is one of the most recognizable constants in physics. In introductory wave questions, it commonly appears in c = fλ for electromagnetic waves in vacuum. It also appears in relativity and in the energy-mass relation E = mc2.
Students sometimes use c in any wave equation, which is a mistake. For ordinary sound waves or waves on a string, the wave speed is not c. Use c only when the situation actually involves electromagnetic radiation in vacuum, or when the course explicitly treats it that way.
If you want the underlying wave relationships reviewed carefully, see Waves Physics Revision Guide: Speed, Frequency, Wavelength, and More.
Electricity and electromagnetism
In electricity, the most common constant students notice is the elementary charge, e. It helps connect charge to the number of electrons transferred: Q = ne. This is especially useful in particle-level electricity questions.
For electric force between point charges, Coulomb’s law uses ke, or equivalently ε0 in a different form. You do not always need to move between those two forms in school-level work, but it helps to know they belong to the same area of electrostatics.
In magnetic topics, μ0 appears in field equations involving current-carrying wires and solenoids. In circuit work, however, many questions can be solved without any fundamental constants at all. They rely more on definitions and relationships such as V = IR, P = IV, and energy equations.
For worked circuit practice, use Ohm’s Law Problems With Answers and Full Working and Electric Circuits Explained: Series vs Parallel With Worked Examples.
Thermal physics
Thermal physics introduces a different style of constant. R, the gas constant, belongs to bulk behavior of gases through pV = nRT. k, the Boltzmann constant, connects temperature to energy per particle. NA, the Avogadro constant, connects moles to actual particle counts.
A useful way to remember them is this:
- Use R when the equation is written in moles.
- Use k when the equation is written per particle.
- Use NA when converting between the two scales.
This pattern matters more than memorizing isolated numbers.
Quantum and modern physics
The Planck constant value, h = 6.63 × 10-34 J·s, is central in modern physics because it links frequency to energy: E = hf. This equation appears simple, but it marks a major shift in how physics describes light and matter. If a question mentions photons, threshold frequency, or emitted radiation from atoms, h is usually nearby.
The elementary charge e also appears here because particle energies are often quoted in electronvolts. Even if your course uses the electronvolt informally, it is still built on the elementary charge.
Radiation and astrophysics
At a slightly more advanced level, the Stefan–Boltzmann constant σ and Wien displacement constant b appear in blackbody radiation. You may not need them every week, but they are good examples of constants that are highly topic-specific. When you see a temperature raised to the fourth power, that is often a clue that σ is involved. When you see peak wavelength multiplied by temperature, that points to b.
Related subtopics
A constants hub becomes much more useful when you connect it to the other study tools you actually use. Here are the related areas that help constants make sense rather than feel like random facts.
Units and prefixes
Many mistakes with constants are really unit mistakes. A constant may be correct, but if the rest of the equation uses centimeters, grams, or nanoseconds without proper conversion, the final answer will be wrong. If you want to tighten that skill, read Physics Units and SI Prefixes Guide: Conversions Students Always Need.
Equation lists and course formula sheets
Different courses expect different levels of memorization. Some provide constants directly; others expect you to know a short list. If you are revising for school exams, compare this hub with your course-specific resources: GCSE Physics Equations List: What You Need to Memorize and What to Understand, A-Level Physics Equations and Constants You Should Know, and AP Physics 1 Formula Sheet Guide: How to Use It Efficiently.
Topic-specific references
Constants become easier to remember when they are attached to repeated use. If SHM is where formulas start to blur together, review Simple Harmonic Motion Explained: Equations, Graphs, and Common Traps. If circuits are your sticking point, work through the circuit guides linked above. The more often you meet a constant in context, the less it feels like something to cram.
A quick distinction: constants vs definitions
Not every familiar quantity is a physical constant. For example, density, resistance, momentum, and kinetic energy are defined quantities, not universal constants. Their formulas describe relationships but do not assign one fixed value across nature. This distinction matters because constants usually belong to your reference sheet, while defined quantities belong to your concept map and formula practice.
How to use this hub
The best way to use a physics reference sheet is not to stare at it passively. Use it to build decision-making during problem solving.
1. Start from the topic, not the symbol
Ask what area of physics the question belongs to: mechanics, waves, electricity, thermal physics, or modern physics. Then ask which constants naturally live in that area. This is much faster than trying to scan your memory for every symbol you have ever seen.
2. Read the unit before the value
The unit often tells you what the constant is doing. For example, h has units of J·s, which hints at energy linked with frequency or time-based behavior. G has units involving force, distance squared, and mass squared, which matches gravitational interaction. If the unit does not fit your equation, pause before calculating.
3. Keep an approximation rule
For many school problems, values are rounded. Common examples are g = 9.8 m/s2 or 10 m/s2, and c = 3.0 × 108 m/s. Use the value your course or exam data sheet expects. Precision should follow the problem, not your guess.
4. Make a two-column revision page
One effective study method is to split your notes into two columns:
- Left: constant, symbol, value, and unit
- Right: one formula and one common use case
For example: c | 3.00 × 108 m/s | c = fλ | electromagnetic waves in vacuum. This format turns a list into a usable memory cue.
5. Practice recognition, not just recall
Instead of only covering the list and testing yourself on values, look at worked questions and ask: which constant should appear here, and why? That habit improves transfer between topics and helps with physics exam prep far more than isolated memorization.
6. Pair constants with solved examples
A constant becomes sticky when you have seen it used correctly several times. If you are building your own physics study guide, keep a small bank of solved examples next to your constants sheet. One gravitation example, one photon-energy example, one charge-quantization example, and one gas-law example go a long way.
When to revisit
This hub is most useful when you return to it at the right moments. Revisit it whenever one of the following happens:
- You begin a new major topic. New sections of a course often introduce a few constants that then appear repeatedly.
- You switch exam levels or syllabuses. The constants emphasized at GCSE, A-Level, AP, or college level are not always the same.
- You notice repeated unit mistakes. A review of constants and units together can fix errors that look like algebra problems.
- You start using a formula sheet. This is the right time to mark which constants are provided and which ones you must recognize on sight.
- Your course expands into newer subtopics. As your physics landscape grows, this list should grow with it.
For a practical next step, do this today: choose five constants from this page, write one formula and one typical question type beside each, and keep that page with your revision notes. Then, when you work through practice problems, pause each time a constant appears and ask what role it is playing. That small habit turns a static list into working understanding.
This is also a hub worth updating over time. As you meet more advanced areas, you can add topic-specific constants rather than cluttering your main notes too early. That keeps your reference sheet lean, accurate, and matched to your current level.
