Nitric Acid Concentration Calculator
Enter a % concentration to get density, specific gravity, g/L, and molarity — or enter a measured density to solve for concentration, up to the ~70% ceiling for aqueous acid.
Where a nitric acid density table actually gets used
Nitric acid does two very different jobs in industry, and both of them lean on exactly this density/concentration relationship. In metal finishing, dilute HNO₃ (roughly 10-30% w/w) strips free iron and surface contamination off stainless steel in a passivation bath — a process standardized under ASTM A967, whose "Nitric 1" and "Nitric 2" baths are conventionally specified as a volume percent of concentrated stock acid, which is a different number from the w/w percentage this calculator solves for (more on that mix-up below). In fertilizer manufacture, "weak nitric acid" (WNA) in the 55-65% range is reacted directly with ammonia to make ammonium nitrate — the acid half of one of the world's highest-volume industrial chemicals — and plants receiving WNA by tanker or storing it in bulk (see this site's tank volume calculator and tank strapping chart calculator for sizing that inventory) routinely spot-check incoming loads with a hydrometer rather than waiting on a lab titration.
Both uses sit comfortably inside this page's 0-70% range. That upper bound isn't arbitrary: aqueous nitric acid has an azeotrope at roughly 68 wt% (boiling at about 121°C), and that's also close to where ordinary commercial "concentrated nitric acid" tops out. Push further — into 90%+ fuming grades used for rocket-propellant oxidizer and specialty nitration chemistry — and the acid starts carrying dissolved NO₂ gas that colors it and changes how density tracks concentration, which is outside what a simple 20°C reference table like this one, or the companion hydrochloric acid and sulfuric acid calculators on this site, are built to represent.
How the calculator gets from one number to the other
The underlying table lists independently measured density values at specific weight-percent points, all at 20°C — the standard reference temperature used across every density table on this site so results stay comparable. Between two adjacent rows, the calculator interpolates linearly rather than fitting one curve across the whole range, because the real concentration-density relationship bends slightly (hydration of the H⁺ and NO₃⁻ ions packs the mixture a bit denser than a straight average would predict) and a short linear segment tracks that bend closely enough for process work.
As a worked example: interpolating for 62% HNO₃ brackets between the 60% row (density 1.3667 g/cm³) and the 65% row (1.3913 g/cm³). The 62% point is 40% of the way across that gap, so density ≈ 1.3667 + 0.4 × (1.3913 − 1.3667) = 1.37654 g/cm³. From there, molarity is a mass balance: a litre of solution weighs 1000 × density grams, the 62% w/w share of that mass is dissolved HNO₃, and dividing by nitric acid's molar mass — 63.012 g/mol, from H (1.008) + N (14.007) + three O (3 × 15.999) — gives roughly 13.54 mol/L.
M = 10 × density × wt% / 63.012
Two shop-floor examples
Mixing a Nitric 1 passivation bath
A finishing shop is qualifying a 316 stainless part per ASTM A967 and wants the density and molarity of a 25% w/w HNO₃ bath to check against their mixing log.
- Concentration
- 25% w/w
- Basis
- 20°C
≈ 1.1469 g/cm³ (SG 1.149), 4.55 mol/L
Spot-checking a tanker of weak nitric acid
An ammonium-nitrate plant's lab dips a hydrometer into an incoming WNA delivery and reads 1.40 g/cm³ — they need the % HNO₃ to confirm it matches the purchase spec before offloading.
- Measured density
- 1.40 g/cm³
- Basis
- 20°C
≈ 66.86% w/w, 14.86 mol/L
Checking the table against a published reference point
Two sanity checks anchor this table against figures that circulate widely in reagent-supplier data sheets and general chemistry references, independent of the specific 20°C source compiled here. First, at 50% w/w the table gives 1.3100 g/cm³, which works out to 10.39 mol/L — this lines up with the "50% nitric acid ≈ 10.4 M" figure commonly quoted for dilution math, a good midpoint check since 50% sits well clear of either table endpoint. Second, at the table's 70% ceiling, the interpolated 1.4134 g/cm³ (SG 1.416) corresponds to about 15.7 mol/L, consistent with the 15.7-16 mol/L range typically reported for reagent-grade concentrated nitric acid across its normal 68-71% assay spread — the small spread there reflects real supplier-to-supplier assay variation, not table error.
Both checks land inside normal rounding and assay tolerance, which is the standard this table is held to: close agreement with independently published concentration/molarity pairs at more than one point across the range, not just at a single convenient anchor.
Reading the result correctly
Weight percent isn't volume percent. This calculator, like the reference table behind it, works entirely in % w/w (mass of HNO₃ per mass of solution). Industrial specs don't always agree — ASTM A967's Nitric 1 and Nitric 2 passivation baths, for instance, are conventionally written as a volume percent of concentrated (68-70%) stock acid, which is a different figure from the resulting bath's w/w assay. If a spec sheet or shop procedure gives you a "%" without saying which basis it means, treat that as a real ambiguity worth resolving before you dose — see this site's dilution math guide and the solution dilution calculator for working through a mass-based dilution from a known stock assay.
Aged acid reads a little off. As covered in the FAQ below, nitric acid slowly decomposes into dissolved NO₂, which shifts its density without being a change in HNO₃ content — a bottle that's visibly yellowed is a signal to titrate rather than trust a density-only read.
Temperature still matters. A sample measured well off 20°C will read slightly dense (cold) or light (hot) for its true concentration — let it equilibrate to room temperature before taking a hydrometer reading if the last digit matters, and note that a colored or fuming sample can also make the meniscus genuinely harder to read accurately.
HNO₃ density reference table (20°C)
| Concentration | Density | Specific gravity | g/L | Molarity |
|---|---|---|---|---|
| 0.00% | 0.9982 g/cm³ | 1.0000 | 0.0 g/L | 0.00 mol/L |
| 5.00% | 1.0256 g/cm³ | 1.0274 | 51.3 g/L | 0.81 mol/L |
| 10.00% | 1.0543 g/cm³ | 1.0562 | 105.4 g/L | 1.67 mol/L |
| 15.00% | 1.0842 g/cm³ | 1.0862 | 162.6 g/L | 2.58 mol/L |
| 20.00% | 1.1150 g/cm³ | 1.1170 | 223.0 g/L | 3.54 mol/L |
| 25.00% | 1.1469 g/cm³ | 1.1490 | 286.7 g/L | 4.55 mol/L |
| 30.00% | 1.1800 g/cm³ | 1.1821 | 354.0 g/L | 5.62 mol/L |
| 35.00% | 1.2140 g/cm³ | 1.2162 | 424.9 g/L | 6.74 mol/L |
| 40.00% | 1.2463 g/cm³ | 1.2485 | 498.5 g/L | 7.91 mol/L |
| 45.00% | 1.2783 g/cm³ | 1.2806 | 575.2 g/L | 9.13 mol/L |
| 50.00% | 1.3100 g/cm³ | 1.3124 | 655.0 g/L | 10.39 mol/L |
| 55.00% | 1.3400 g/cm³ | 1.3424 | 737.0 g/L | 11.70 mol/L |
| 60.00% | 1.3667 g/cm³ | 1.3692 | 820.0 g/L | 13.01 mol/L |
| 65.00% | 1.3913 g/cm³ | 1.3938 | 904.3 g/L | 14.35 mol/L |
| 68.00% | 1.4053 g/cm³ | 1.4078 | 955.6 g/L | 15.17 mol/L |
| 70.00% | 1.4134 g/cm³ | 1.4159 | 989.4 g/L | 15.70 mol/L |
Sources: Density–concentration data: compiled aqueous nitric acid density reference at 20 °C, anchored at 0 wt% with the standard water density constant 0.9982 g/cm³. Cross-checked by back-calculating molarity at each row and comparing against the concentration/molarity pairs (≈10.4 mol/L at 50%, ≈15.7-16 mol/L for concentrated 68-71% assay acid) commonly published in reagent-supplier references. Table bounded at 70% w/w — see the scope note above for why fuming grades are excluded.
Frequently asked questions
Why does this table stop at 70% instead of going up to 100%?
Above roughly 68 wt% you're past the HNO3-water azeotrope, and aqueous nitric acid stops behaving like a simple water dilution — the concentrated grades beyond that (fuming nitric acid, both white and red) carry dissolved NO2 gas that colors the liquid and changes its density behavior independently of water content. That's a distinct, unstable specialty product mostly used in propellant and specialty-synthesis work, not something a standard 20°C reference table can represent with the same simple interpolation. 0-70% w/w covers essentially every etching, passivation, pickling, and fertilizer-feedstock use of nitric acid, which is why the table is bounded there rather than guessed at further.
My drum or COA says '68-70% nitric acid' — which number do I enter?
Suppliers often quote concentrated nitric acid as a range because that's genuinely how it's produced and sold — it's the azeotropic/commercial grade, not a single fixed assay. If you have a certificate of analysis, use its stated assay percentage. If you only have the drum label's range, entering the low end (68%) gives you a conservative (slightly weaker) estimate for dosing math; for anything where the exact number matters — a passivation spec, a titration cross-check, a shipment weight — pull the COA or titrate a sample rather than assuming the midpoint.
Is nitric acid graded in degrees Baumé, like the HCl and H2SO4 pages on this site?
Yes, historically. The conversion is the same heavy-Baumé formula used throughout this site's other acid calculators: °Bé = 145 − (145 / SG), or reversed, SG = 145 / (145 − °Bé). "42° Baumé nitric acid" is the long-standing trade name for the concentrated stock acid that passivation shops dilute down to make ASTM A967's Nitric 1 and Nitric 2 baths, and it lines up almost exactly with this table's 68% row: SG 1.408 run through the formula above gives °Bé ≈ 42.0. This calculator reports density and SG directly, so run either figure through the formula above if you're matching an old Baumé-marked hydrometer or a legacy spec sheet.
My old bottle of nitric acid has turned yellow — does that throw off a density-based reading?
It can, and it's worth knowing why. Nitric acid slowly decomposes under light and heat: 4 HNO3 → 4 NO2 + O2 + 2 H2O. The NO2 stays dissolved and turns the acid yellow, then amber, then brown as more accumulates. That dissolved NO2 adds mass to the solution without being HNO3, so a hydrometer or this calculator's density lookup reads a blend of "real acid strength" and "how much it has decomposed," not pure concentration. A faint yellow tint from normal aging usually isn't enough to matter for shop-floor dosing, but a genuinely brown, fuming bottle should be titrated rather than trusted to a density chart — and note that decomposition also means the bottle is now generating gas pressure, which is its own handling concern independent of the math.
What is the difference between density and specific gravity here?
Density is mass per volume with real units (g/cm³). Specific gravity (SG) is that same density divided by the density of water at a reference condition — 20°C water at 0.9982 g/cm³ throughout this site. Because water's density sits so close to 1, density in g/cm³ and SG come out numerically close for an aqueous acid, but a hydrometer marked "SG" is reading that ratio directly, not grams per millilitre — worth knowing if you're cross-referencing an instrument spec sheet against this calculator's g/cm³ output.
How accurate is a value the calculator interpolates between two rows?
This table steps in 5-percentage-point increments (with an extra row at the 68% azeotrope point) rather than the 1-point or finer steps used on this site's HCl and H2SO4 tables — nitric acid's density curve is smooth and gently curved over this range, so a straight line between points 5% apart introduces only a very small error, well inside normal field-measurement uncertainty from a hydrometer or refractometer. For routine dosing, bath makeup, and QC checks that's more than tight enough; if you need a certified figure for a shipment or a regulatory filing, confirm with a lab titration rather than relying on any density-based estimate, this one included.