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Kilodaltons to Daltons Converter
↔ Convert Da to kDa instead

Common Conversions

kDa Da
0.1 100
0.5 500
1 1000
5 5000
10 10000
25 25000
50 50000
66.5 66500
100 100000
150 150000
500 500000
1000 1000000

Why this conversion matters in chemistry

Antibody intact-mass characterization runs across this conversion. An IgG1 therapeutic written as 148.5 kDa in the structural literature shows up as a 148,500 Da peak (or a series of glycoform peaks separated by ~162 Da each for hexose mass) on a deconvoluted intact-mass ESI-MS spectrum. The multiplier of 1000 falls cleanly out of the kilo prefix. What it really is: the unit jump between the kDa convention biochemists use for protein-scale molecules and the Da resolution mass spectrometry actually measures.

Formula

Da = kDa × 1000

Worked Examples

66.5 kDa = 66500 Da

BSA — the calibration anchor for many protein-mass quantitation curves.

1 kDa = 1000 Da

The factor anchor — about a 9-residue peptide expressed in Da.

150 kDa = 150000 Da

An IgG antibody — the per-Da figure for an intact-mass measurement.

10 kDa = 10000 Da

A 10 kDa MWCO ultrafiltration cutoff — the membrane spec written in Da on the cassette.

Frequently Asked Questions

How do I convert kDa to Da?
Multiply by 1000. So 150 kDa becomes 150,000 Da — an IgG antibody. The factor is exact through the kilo prefix.
When is the dalton needed instead of kDa?
Intact-mass and top-down mass spectrometry report in Da to capture the per-Da resolution of the measurement. Molarity calculations from a mass concentration also need Da (or g/mol) in the denominator. SDS-PAGE estimates work in kDa because the gel resolves no better.
What's a megadalton?
1 MDa = 1,000,000 Da = 1000 kDa. The MDa scale describes ribosomes (~2.5 MDa), viral capsids, and supramolecular complexes — assemblies too large for the kDa scale to read cleanly.