Concentration Unit Converter
How to use: enter a concentration value and select its unit. All equivalent concentrations update instantly. Pick a reagent to auto-fill its molecular weight, or type a custom MW for molar conversions.
Reagent (auto-fills MW)
Quick Picks
Concentration Value
Molecular Weight (g/mol) ?
NaCl (58.44 g/mol)
Density (g/mL) ?
Dilution Calculator (C1V1 = C2V2)
Target Concentration
Final Volume
Stock volume needed--
Diluent to add--
Dilution factor--
0.05844
mg/mL
1 mM NaCl (MW 58.44)
—
Molarity (M)
—
mg/mL
—
% w/v
—
ppm
Molar Concentrations
Mass / Volume Concentrations
Percent & Parts Notation

About Concentration Unit Conversion in Life Sciences

This concentration unit converter handles the unit conversions that bench scientists perform daily: molarity to mg/mL, mg/mL to % w/v, ppm to molarity, and every other combination of concentration units used in biology and chemistry laboratories. The built-in molecular weight library covers 50+ common reagents, from buffers (Tris, HEPES, MOPS) and salts (NaCl, KCl, MgCl2) to antibiotics (ampicillin, kanamycin, puromycin), proteins (BSA, IgG, lysozyme), and inducers (IPTG). For proteins not in the library, the protein MW calculator computes the molecular weight from an amino acid sequence.

The most common conversion mistake in the lab is between % w/v and mg/mL. Percent w/v means grams per 100 mL, so 1% w/v = 10 mg/mL (not 1 mg/mL). Similarly, converting between molar and mass concentration always requires the molecular weight: mg/mL = M × MW. For a 150 kDa IgG antibody, 1 mg/mL is only 6.67 µM, while for a small molecule like IPTG (MW 238.3), 1 mg/mL is 4.20 mM. Getting this conversion right matters for dosing accuracy, buffer preparation, and regulatory documentation in GMP environments.

For buffer recipe preparation, use the buffer calculator or browse the buffer recipe database. The molarity calculator solves for mass, volume, or concentration when preparing molar solutions from scratch. For protein quantification workflows, the protein concentration calculator handles BCA, Bradford, and A280 assay data.

Further reading

Related Articles

Buffer Preparation Guide
Step-by-step protocols for common laboratory buffers
Essential Bioprocess Formulas
Key equations for upstream, downstream, and analytical calculations
BCA Assay Calculation Guide
Standard curve fitting and protein quantification from absorbance data
High-Concentration Antibody Formulation
Strategies for formulating mAbs above 100 mg/mL

Frequently Asked Questions

How do I convert molarity to mg/mL?

Multiply molarity by molecular weight: mg/mL = M × MW (g/mol). For example, 1 mM NaCl (MW 58.44) = 0.001 × 58.44 = 0.05844 mg/mL. For proteins, 1 mg/mL of a 150 kDa IgG equals 1/150,000 = 6.67 µM. You always need the molecular weight to convert between molar and mass concentration units.

What is the difference between % w/v and mg/mL?

Percent w/v (weight/volume) means grams of solute per 100 mL of solution. To convert: mg/mL = % w/v × 10. So 1% w/v = 10 mg/mL, and 0.05% Tween 20 = 0.5 mg/mL. This is the most common source of bench errors because the factor of 10 is easy to forget.

How do I convert ppm to mg/mL?

For aqueous solutions (density ≈ 1 g/mL), 1 ppm = 1 mg/L = 0.001 mg/mL. So mg/mL = ppm / 1000. For example, 500 ppm = 0.5 mg/mL. This equivalence assumes water density; for non-aqueous solvents, multiply ppm by the solution density (g/mL) and divide by 1000.

Do I always need molecular weight to convert concentration units?

No. Conversions within mass-based units (mg/mL, µg/mL, g/L, % w/v, ppm, ppb) do not require MW. Molecular weight is only needed when converting between molar units (M, mM, µM, nM) and mass units. For example, mg/mL to % w/v is just dividing by 10, with no MW needed.

How do I prepare a dilution from a stock solution?

Use the dilution equation C1 × V1 = C2 × V2. Enter your stock concentration (C1), target concentration (C2), and final volume (V2). The calculator gives the stock volume needed (V1 = C2 × V2 / C1) and the diluent volume (V2 − V1). For example, to make 10 mL of 1 mM from a 100 mM stock: V1 = 1 × 10 / 100 = 0.1 mL stock + 9.9 mL diluent.

What is the difference between ppm and ppb?

PPM (parts per million) and PPB (parts per billion) differ by a factor of 1000: 1 ppm = 1000 ppb. In aqueous solutions, 1 ppm = 1 mg/L and 1 ppb = 1 µg/L. PPM is common for media supplements, buffer additives, and water quality (e.g., 100 ppm iron). PPB is used for trace contaminants like leachables from single-use systems or residual DNA.