NGS library concentration converter — Convert dsDNA library between mass (ng/µL) and molarity (nM) for sequencer loading. Formula: nM = (ng/µL × 10⁶) / (660 × avg fragment length). 660 g/mol/bp is the average dsDNA base-pair MW.

(1) Convert dsDNA library mass concentration and molarity (2) Prepare inputs for pre-multiplex normalization and pooling calculations (3) Compare expected and measured library-prep yield (4) Prepare concentration values for the current instrument-, flow-cell-, and chemistry-specific loading guide

① Enter library concentration (ng/µL — Qubit reading) ② Enter average fragment length (bp — TapeStation/Bioanalyzer peak size) ③ Choose direction (ng/µL → nM or nM → ng/µL) ④ Result auto-displays Note: Use total length including adapters (e.g., 350 bp insert + 120 bp adapter = 470 bp) for accuracy. qPCR-based KAPA library quant is more precise; this tool is for quick conversion.

Example 1) RNA-seq library, Qubit 15 ng/µL, total length 350 bp → nM = (15 × 10⁶) / (660 × 350) = 64.9 nM → Select the next dilution/loading target from the current kit, instrument, and flow-cell guide Example 2) Pooling — Library A 20 nM × 50 µL + Library B 10 nM × ? → For equimolar pooling, use 100 µL of B