Molar mass is the mass in grams of one mole (6.022 × 10²³ particles) of a substance. It numerically equals the molecular weight in atomic mass units (amu).

Why are atomic weights decimal numbers?

Atomic weights are weighted averages of all naturally occurring isotopes of an element, so they are rarely whole numbers.

What elements are supported?

H, C, N, O, Na, Cl, K, Ca, Fe, S, P, Mg, Al, Si, F, Br, I. More common in biochemistry and general chemistry.

Does it support parentheses?

Not currently — expand parenthetical groups manually. For Ca3(PO4)2, enter Ca3P2O8 (3 Ca + 2 P + 8 O).

How do I calculate the formula weight of an ionic compound?

Use the same approach — NaCl is Na1Cl1. The formula weight and molecular weight are calculated identically.

Everyday

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Molecular Weight Calculator - Molar Mass Formula Online

Calculate the molecular weight of any chemical compound by entering its formula, with a full element breakdown.

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How to use this calculator

👉 Fill in the boxes below and your answer appears instantly — no maths needed, we do it all for you! 🎉

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In plain English — what does this do?

🏋️ Your body needs food to move, breathe, and grow — just like a car needs petrol. This tool helps you find out how much food your body needs in a day to feel good and stay healthy!

📌 Direct Answer & Summary

The Molecular Weight Calculator computes the molar mass of a chemical compound from its molecular formula. Enter a formula like H2O, NaCl, or C6H12O6 and the calculator parses each element and its count, then multiplies by standard atomic weights to produce the total molecular weight in g/mol.

Chemical Formula

What is Molecular Weight Calculator - Molar Mass Formula Online?

How to use it

1️⃣ Type the chemical formula into the input field, e.g. H2O, NaCl, C6H12O6.
2️⃣ Use standard element symbols with capital first letters (e.g. Na, not na).
3️⃣ Add subscript numbers directly after the element symbol (e.g. H2, O3).
4️⃣ Click Calculate to see the molecular weight and a breakdown by element.
5️⃣ Parentheses are not supported — expand them manually (e.g. Ca3(PO4)2 → Ca3P2O8).

Formula

Molecular weight = Σ (atomic weight of element × count). Atomic weights used: H=1.008, C=12.011, N=14.007, O=15.999, Na=22.990, Cl=35.45, K=39.098, Ca=40.078, Fe=55.845, S=32.06, P=30.974, Mg=24.305, Al=26.982, Si=28.086, F=18.998, Br=79.904, I=126.90.

💡 See it in action — a real example

C6H12O6 (glucose): 6×12.011 + 12×1.008 + 6×15.999 = 72.066 + 12.096 + 95.994 = 180.156 g/mol.

❓ Common questions

What is molar mass?: Molar mass is the mass in grams of one mole (6.022 × 10²³ particles) of a substance. It numerically equals the molecular weight in atomic mass units (amu).
Why are atomic weights decimal numbers?: Atomic weights are weighted averages of all naturally occurring isotopes of an element, so they are rarely whole numbers.
What elements are supported?: H, C, N, O, Na, Cl, K, Ca, Fe, S, P, Mg, Al, Si, F, Br, I. More common in biochemistry and general chemistry.
Does it support parentheses?: Not currently — expand parenthetical groups manually. For Ca3(PO4)2, enter Ca3P2O8 (3 Ca + 2 P + 8 O).
How do I calculate the formula weight of an ionic compound?: Use the same approach — NaCl is Na1Cl1. The formula weight and molecular weight are calculated identically.

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