Chemical Equation Balancer
Balance any chemical equation instantly. Type or build the equation, and the balancer finds the smallest whole-number coefficients, names the reaction type, explains every step, and opens a stoichiometry calculator with limiting reagent. Everything runs in your browser, free, with no sign-up.
Free Online Chemical Equation Balancer
This chemical equation balancer finds the smallest whole-number coefficients for any reaction in a fraction of a second and shows every step of the work. Type an unbalanced equation such as Fe + O2 = Fe2O3, press Enter, and you get the balanced chemical equation, the reaction type, a step-by-step explanation and a stoichiometry calculator with limiting reagent. Everything runs in your browser, with no sign-up.
It handles everything from a first-year chemistry equation like the synthesis of water to redox reactions with large coefficients, ionic equations with charges, hydrates and formulas with parentheses. Students use it to check homework, teachers use it to build worked examples, and anyone can use it to learn how balancing chemical equations actually works.
How to Balance Chemical Equations Step by Step
Balancing a chemical equation means choosing coefficients so that every element has the same number of atoms on both sides of the arrow. Atoms are never created or destroyed in a reaction, only rearranged, so a correct equation obeys the law of conservation of mass. Here is the method, using the combustion of propane as the example.
- Write the unbalanced equation with the correct formula for every substance:
C3H8 + O2 → CO2 + H2O. Never change a subscript to balance an equation; that would change the substance itself. - Count the atoms of each element on both sides. Left: 3 C, 8 H, 2 O. Right: 1 C, 2 H, 3 O.
- Balance one element at a time, starting with the one that appears in the fewest places. Carbon: put a 3 in front of CO2. Hydrogen: put a 4 in front of H2O.
- Balance oxygen last, because it now appears in three compounds. The right side has 6 + 4 = 10 oxygen atoms, so O2 needs a coefficient of 5.
- Check the result and make sure the coefficients are the smallest whole numbers:
C3H8 + 5O2 → 3CO2 + 4H2O. Both sides now have 3 C, 8 H and 10 O.
Tips that make balancing faster
- Balance metals first, then non-metals, and leave hydrogen and oxygen for the end.
- Treat polyatomic ions such as SO4 or NO3 as one unit when they appear unchanged on both sides.
- If you end up with a fraction, multiply every coefficient by its denominator.
- For ionic and redox equations, check that the total charge balances as well as the atoms.
- When an element appears in several compounds on one side, balance the most complex compound first.
Types of Chemical Reactions You Can Balance
After balancing, the tool identifies the reaction type and explains it. It recognizes:
- Combustion: a fuel reacts with oxygen, for example CH4 + 2O2 → CO2 + 2H2O
- Synthesis: two or more substances form a single product, for example N2 + 3H2 → 2NH3
- Decomposition: one compound breaks apart, for example 2H2O2 → 2H2O + O2
- Single replacement: one element displaces another, for example Zn + 2HCl → ZnCl2 + H2
- Double replacement: two compounds swap partners, for example AgNO3 + NaCl → AgCl + NaNO3
- Acid-base neutralization, for example HCl + NaOH → NaCl + H2O
- Redox: electrons are transferred, for example 2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2
- Precipitation and gas evolution, including net ionic equations such as Ag+ + Cl− → AgCl
Stoichiometry Calculator with Limiting Reagent
Every balanced equation opens a stoichiometry calculator. Enter the amount of any reactant or product in moles or grams and the calculator fills in every other substance, using the mole ratio from the coefficients and the molar masses from the periodic table.
When you enter amounts for more than one reactant, it finds the limiting reagent, the reactant that runs out first, and uses it to calculate the theoretical yield of each product and how much of the excess reagents is left over. That is exactly the calculation behind most stoichiometry homework problems.
Worked Examples
Common balanced chemical equations. Type any of these into the balancer above to see the full step-by-step solution.
2H2 + O2 → 2H2OSynthesis of waterCH4 + 2O2 → CO2 + 2H2OCombustion of methaneC3H8 + 5O2 → 3CO2 + 4H2OCombustion of propaneN2 + 3H2 → 2NH3Ammonia synthesis (Haber process)2H2O2 → 2H2O + O2Decomposition of hydrogen peroxideCaCO3 → CaO + CO2Decomposition of calcium carbonate
Browse all balanced equations
Frequently Asked Questions
What is a balanced chemical equation?
A balanced chemical equation has the same number of atoms of each element on both sides of the reaction arrow. This follows the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a chemical reaction. For example, in 2H2 + O2 = 2H2O, there are 4 hydrogen atoms and 2 oxygen atoms on each side.
How do you balance a chemical equation?
To balance a chemical equation manually: 1) Write the unbalanced equation with correct formulas. 2) Count atoms of each element on both sides. 3) Add coefficients (numbers in front of formulas) to balance one element at a time. 4) Start with the most complex molecule. 5) Balance hydrogen and oxygen last. 6) Verify all elements are balanced and coefficients are the smallest whole numbers.
Why do chemical equations need to be balanced?
Chemical equations must be balanced because atoms are neither created nor destroyed during reactions - they are only rearranged. An unbalanced equation violates the Law of Conservation of Mass and does not accurately represent the reaction. Balanced equations are essential for calculating reactant and product quantities in stoichiometry.
What is stoichiometry?
Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. Using the mole ratios from a balanced equation, you can calculate how much of each substance is needed or produced. This is crucial for laboratory work, industrial processes, and understanding reaction yields.
What is a limiting reagent?
The limiting reagent (or limiting reactant) is the substance that is completely consumed first in a chemical reaction, determining the maximum amount of product that can be formed. Once the limiting reagent is used up, the reaction stops - even if other reactants remain. The leftover reactants are called excess reagents.
What types of reactions can this chemical reaction balancer solve?
This balancer handles all types of chemical equations including combustion, synthesis, decomposition, single replacement, double replacement, acid-base, redox, and precipitation reactions. It uses matrix algebra to find the smallest whole-number coefficients for any valid chemical equation.
Is this chemical equation balancer free?
Yes. There is no sign-up, no limit on the number of equations and no ads. Everything runs in your browser, so the equations you type are never sent to a server.
Can it balance redox and ionic equations?
Yes. Write charges after the formula, such as Fe3+ or MnO4-, and the balancer conserves charge as well as atoms. Half-reactions with electrons written as e- work too.
Why does it say an equation cannot be balanced?
Usually because an element appears on only one side of the arrow, or a product is written where a reactant belongs. The error message names the compound so you can fix the formula. Check the formulas first: balancing never changes subscripts.
Can I scan a handwritten equation?
Yes. On a phone, tap Scan, fit the equation inside the frame and take the picture. The equation is read into the input box for you to check, then balanced as usual. It works with handwriting and printed text, ions and coefficients. The photo is processed in memory and not stored, and each visitor gets 20 scans a day.