A mole is a count and a gram is a mass, so nothing bridges them but the substance. Two more quantities that look interchangeable — molarity and molality — need a third one nobody mentions.
Calculator
Try:
10 g of Sodium chloride
0.17111 mol
That is 1.0304 × 10^23 molecules — the Avogadro constant has been exactly 6.0221 × 10^23 per mole since the 2019 redefinition, so this figure is definitional rather than measured.
The same 10 g, of different substances
Why there is no grams-to-moles factor
Substance
Molar mass
Moles
Water (H₂O)
18.015 g/mol
0.55509
Sodium chloride (NaCl)
58.443 g/mol
0.17111
Glucose (C₆H₁₂O₆)
180.156 g/mol
0.05551
Sodium hydroxide (NaOH)
39.997 g/mol
0.25002
Hydrochloric acid (HCl)
36.458 g/mol
0.27429
Sulphuric acid (H₂SO₄)
98.079 g/mol
0.10196
Calcium carbonate (CaCO₃)
100.087 g/mol
0.09991
Potassium chloride (KCl)
74.551 g/mol
0.13414
Ammonia (NH₃)
17.031 g/mol
0.58716
Ethanol (C₂H₅OH)
46.069 g/mol
0.21707
A tenfold spread across ordinary laboratory substances. Ammonia and glucose differ by more than ten times in molar mass, so the same mass on the balance is ten times the amount of substance. This is why the molar mass is a required input here rather than a default.
Making it into a solution
Molarity0.3422 mol/Lmoles per litre of solution
Molality0.3257 mol/kgmoles per kg of solvent — -5.07% apart
Normality0.3422 N× 1 equivalent per mole
To make this from scratch10.000 gmade up to 0.5 L
Molarity counts per litre of solution; molality counts per kilogram of solvent. Converting between them needs the density — a third quantity neither name mentions — and the gap grows with concentration. Molarity also drifts with temperature, because volume expands and mass does not, which is why physical chemistry works in molality.
How far apart they get
Sodium chloride in water at 20 °C, using measured densities
Strength
Density
Molarity
Molality
Apart by
1% w/w
1.0053
0.172
0.173
0.48%
5% w/w
1.034
0.885
0.901
1.77%
10% w/w
1.0707
1.832
1.901
3.64%
20% w/w
1.1478
3.928
4.278
8.18%
26% w/w
1.1972
5.326
6.012
11.41%
Half a per cent in a dilute solution, over eleven near saturation. The densities here are published measurements at 20 °C rather than a fitted curve, because the whole point of the table is that the divergence is real.
“10% solution” is three solutions
10% wv of Sodium chloride1.7111 mol/Lneeds only the molar mass
The same 10% read as w/v gives 1.7111 M and read as w/w gives 1.8320 M. They coincide only when the density is exactly one, which is to say only for dilute aqueous solutions — the case everyone generalises from.
Diluting a stock
Make up to400.0 mLC₁V₁ = C₂V₂
Solvent to add300.0 mLapproximately — volumes are not strictly additive
The second row is the one to treat as a guide rather than an instruction. Mixing two liquids does not give the sum of their volumes, so a dilution is made by adding solvent up to the mark, not by adding a measured amount to the stock. For concentrated acids the rule is stronger still: always add the acid to the water.
What this converter covers
Grams, moles and molecules; molarity, molality and normality; the three readings of a percentage; and a dilution done properly.
Grams to moles and back for any molar mass, with ten common substances built in
The number of molecules, from the exactly defined Avogadro constant
Molarity, molality and the density that bridges them
w/v, w/w and v/v percentages, and which of them convert
Normality, and the C₁V₁ = C₂V₂ dilution
Molar mass required Density required Three kinds of % Dilution and recipe
Free, no signup — exact by definition, not an estimate.
Updated 8 September 2026
At a glance
Formula shown
n = m ÷ M · c = n ÷ V(solution) · b = n ÷ m(solvent) · N = c × equivalents
Scenario support
10 g is 0.55 mol of ammonia and 0.055 of glucose · 26% brine is 5.33 M and 6.01 molal
Educational estimate
Planning support from the values you enter — not professional advice.
There is no grams-to-moles factor
A mole is a count: exactly 6.02214076 × 10²³ things. A gram is a mass. Nothing converts one into the other except the mass of one mole of the particular substance — which is different for every substance.
Ten grams, of ten ordinary laboratory substances
Substance
Molar mass
Moles in 10 g
Ammonia (NH₃)
17.031
0.587
Water (H₂O)
18.015
0.555
Hydrochloric acid (HCl)
36.458
0.274
Sodium hydroxide (NaOH)
39.997
0.250
Sodium chloride (NaCl)
58.443
0.171
Sulphuric acid (H₂SO₄)
98.079
0.102
Glucose (C₆H₁₂O₆)
180.156
0.056
A tenfold spread. Ten grams of ammonia is ten times the amount of substance that ten grams of glucose is, and any reaction is counting molecules rather than weighing them — which is the entire reason the mole exists as a unit.
So this converter requires a molar mass and refuses without one. It is a small friction and the alternative is worse: a tool that quietly assumed water would produce a confident number for every question and be right for one substance.
Two things about molar masses are worth knowing. They are computed from atomic weights rather than measured, so they carry no experimental uncertainty worth worrying about at bench precision. And they are for the pure, anhydrous substance — a hydrated salt such as copper sulphate pentahydrate weighs a great deal more per mole than the anhydrous figure, and using the wrong one is a large error that produces a plausible-looking solution.
Molarity is not molality
Two words that differ by two letters, two symbols that differ by a case, and two quantities that are genuinely different.
Molarity is moles per litre of solution — the finished thing, solute included. Molality is moles per kilogram of solvent— just the water, before anything was added. Converting between them requires the solution’s density, which neither name mentions and which most sources omit.
Sodium chloride in water at 20 °C, using measured densities
Strength
Density
Molarity
Molality
Apart by
1% w/w
1.0053
0.172
0.173
0.48%
5% w/w
1.0340
0.885
0.901
1.77%
10% w/w
1.0707
1.832
1.901
3.64%
20% w/w
1.1478
3.928
4.278
8.18%
26% w/w
1.1972
5.326
6.012
11.41%
In a dilute solution they agree to within half a per cent, which is why the two get treated as interchangeable and why the habit survives — most bench work is dilute and aqueous. Near saturation they are 11% apart, and at that point the choice is not a detail.
The direction is always the same for a solute denser than the solvent it displaces: molarity comes out lower, because a litre of solution contains less than a kilogram of solvent. The densities in the table above are published measurements rather than a fitted curve, because the whole claim is that the divergence is real.
Only one of them survives a temperature change
There is a second, sharper difference between the two, and it is the reason physical chemistry prefers molality while every bench protocol is written in molarity.
Molarity is defined per unit volume, and volume expands when warmed. A solution made up to exactly 1.000 M at 20 °C is no longer 1.000 M at 50 °C — nothing has been added or removed, but the flask holds a larger volume of the same material, so the concentration has fallen. Molality is defined per unit mass, and mass does not care about temperature at all.
For water the effect is small over ordinary laboratory ranges — a few tenths of a per cent — and it is routinely ignored. It stops being ignorable in three places: work at elevated temperature, work demanding better than about half a per cent, and any calculation of a colligative property. Freezing-point depression and boiling-point elevation are proportional to molality precisely because using molarity would make the constant depend on temperature, which is exactly the thing the constant is supposed to remove.
The practical reading: use molarity for making things up and for stoichiometry at a known temperature, which is nearly everything. Reach for molality when the temperature moves, when the answer needs to be better than a per cent, or when a textbook formula asks for it — and notice that it is asking for a different quantity rather than the same one under another name.
“10% solution” is three solutions
A percentage concentration can be mass in volume, mass in mass or volume in volume, all written the same way, and they are not equal.
“10% sodium chloride”, read three ways
Basis
Means
Molarity
Needs
w/v
10 g per 100 mL of solution
1.711 M
Molar mass
w/w
10 g per 100 g of solution
1.832 M
Molar mass and density
v/v
10 mL per 100 mL of solution
—
The pure solute’s own density
The first two differ by 7% for this solution, and the gap is simply the density: a litre of 10% brine weighs 1071 g rather than 1000, so the same mass fraction is more solute per litre. They coincide only when the density is exactly one — dilute aqueous solutions, which is the case everyone generalises from.
The third does not convert at all without knowing the density of the pure solute, and this calculator returns nothing rather than assuming one. It is also the least well-defined of the three: volumes are not additive on mixing, so 10 mL of ethanol plus 90 mL of water is not 100 mL of solution, and a v/v figure is a nominal recipe rather than a measurable composition.
Some conventions make it worse. Clinical chemistry writes “g%” for w/v; some industries write “%” meaning w/w without saying so; and concentrated reagents are almost always w/w while their working dilutions are w/v. When a percentage matters, the basis has to be stated — and if a source does not state it, that is a question rather than an assumption.
Normality depends on the reaction
Normality is molarity multiplied by the number of reactive units each molecule supplies. It is convenient for titration arithmetic and it carries a trap: that number is a property of the reaction, not of the substance.
One molar, in normality
Substance
Equivalents per mole
1 M is
Hydrochloric acid
1 proton
1 N
Sodium hydroxide
1 hydroxide
1 N
Sulphuric acid
2 protons
2 N
Calcium carbonate
2 charges
2 N
So “0.1 N sulphuric acid” is 0.05 M, and treating the two figures as the same halves or doubles every result that follows. The classic failure is transcribing a normality from an older method into a modern protocol written in molarity without noticing the label changed.
The deeper problem is that a substance can have more than one normality. Sulphuric acid is 2 N when both protons react and 1 N in a reaction that takes only the first. Potassium permanganate is 5 N in acid and 3 N in neutral conditions, because the manganese ends up in a different oxidation state. The number is not a property you can look up without knowing what is happening.
This is why IUPAC recommends stating the reaction and using molarity instead, and why this calculator asks for the equivalents rather than assuming them. Normality is not wrong — it is a genuine convenience in titration work — but it is only meaningful alongside the reaction it was defined for.
Related calculators
Other concentration and laboratory tools:
PPMppm to percent, mg/L and µg/m³ — asking which liquid or which gas, because without that the conversion has no answer.
Water Hardnessppm, gpg, °dH, °fH and °e — every factor derived from molar masses, plus the calcium and magnesium a lab actually reports.
Densitykg/m³, lb/ft³, lb/in³ and lb/gal, with specific gravity against any water reference and the API scale that runs backwards.
VolumeLitres, gallons, pints and cubic units — with US and imperial named apart, because a UK gallon is 20% larger than a US one.
WeightKilograms, pounds, ounces, stone and tonnes, listing the short, long and metric ton separately — three masses, one word.
Scientific NotationScientific, engineering and decimal forms with significant figures counted — and ambiguous inputs flagged rather than silently resolved.
The mole has been defined since 2019 as exactly 6.02214076 × 10²³ entities, so the Avogadro constant on this page is a definition rather than a measurement — a change that also detached the mole from carbon-12. The distinction between amount concentration and molality is IUPAC’s, as is the position that normality should be replaced by stating the reaction, which is why this page asks for the equivalents rather than assuming them.
SI Brochure, 9th edition — the definition of the moleBureau International des Poids et Mesures · verified 2026-09-08 · That since the 2019 revision the mole is defined as exactly 6.022 140 76 × 10²³ elementary entities, so the Avogadro constant is exact by definition rather than measured against carbon-12
IUPAC Compendium of Chemical Terminology (the Gold Book)International Union of Pure and Applied Chemistry · verified 2026-09-08 · The definitions of amount concentration (molarity, per volume of solution) and molality (per mass of solvent) as separate quantities, and IUPAC’s deprecation of normality in favour of stating the reaction explicitly
IUPAC standard atomic weightsInternational Union of Pure and Applied Chemistry · verified 2026-09-08 · The atomic weights every molar mass on this page is summed from — a molar mass is a computed figure rather than a measured property of any particular sample
Conversion note
This is solution arithmetic, not a laboratory protocol. The molar masses are computed from standard atomic weights for pure, anhydrous substances — a hydrated salt, a technical grade, or anything that has taken up water from the air has a different effective mass, and using the anhydrous figure for a hydrate is a common and large error. Densities vary with temperature and with the exact composition, and the reference values here are for sodium chloride in water at 20 °C. Volumes are not additive on mixing, so a dilution is made by adding solvent up to a calibrated mark rather than by adding a measured amount to the stock. Concentrated acids and bases, and any reaction that evolves heat or gas, need the handling and protective equipment set out in the relevant safety data sheet — always add acid to water, never the reverse. Nothing here is a substitute for a validated method where a result has clinical, regulatory or safety consequence.
Published the Moles to Grams Converter: grams, moles and molecules, with molarity, molality, normality, the three percentage bases and a dilution.
Establishes that grams do not convert to moles at all -- a mole is a count and a gram is a mass -- and requires a molar mass rather than defaulting to water, since the same 10 grams is a tenfold range of moles across ordinary laboratory substances.
Notes that a molar mass is computed from atomic weights rather than measured, and that it is for the pure anhydrous substance, so using an anhydrous figure for a hydrated salt is a large error that produces a plausible-looking solution.
Separates molarity, which is moles per litre of solution, from molality, which is moles per kilogram of solvent, and requires the solution density to bridge them -- a third quantity neither name mentions.
Shows the divergence growing with concentration using published sodium chloride densities at 20 degrees rather than a fitted curve: 0.48 percent apart in 1 percent brine and 11.41 percent apart near saturation.
Explains the sharper difference that decides which unit a discipline uses: molarity is per unit volume and volume expands when warmed, while molality is per unit mass and does not -- which is why colligative properties are proportional to molality.
Sets out that a percentage concentration is three different quantities written the same way, and that the same 10 percent sodium chloride is 1.711 molar read as w/v and 1.832 read as w/w, a 7 percent gap that is simply the density.
Refuses a volume-per-volume percentage outright rather than inventing a solute density, and notes that volumes are not additive on mixing so a v/v figure is a nominal recipe rather than a measurable composition.
Treats normality as molarity times a REACTION-dependent factor rather than a substance property: 0.1 normal sulphuric acid is 0.05 molar, and permanganate is 5 normal in acid and 3 in neutral conditions.
Uses the exactly defined Avogadro constant, 6.02214076 times ten to the 23rd, which has been a definition rather than a measurement since the 2019 SI revision detached the mole from carbon-12.
Warns that a dilution is made by adding solvent up to a calibrated mark rather than by adding a measured amount to the stock, and that acid is always added to water.
Verified by 52 automated cases, asserting that grams and moles refuse without a molar mass, that the molarity-molality gap widens monotonically across five measured densities rather than being checked at one point, and that v/v returns nothing.
Add this calculator to your site
Responsive embed — and private: nothing your visitors type leaves their browser.