Sequencing Depth & Data Volume Calculator (Lander-Waterman)

Sequencing depth (coverage / depth) is defined by the Lander-Waterman model:

C = N × L / G

• C: mean coverage, expressed as 30×, 100×, etc.
• N: number of reads
• L: read length (for paired-end sequencing, total length of both strands; PE150 = 300 bp)
• G: genome (or target region) size

Conversely, the data volume required to reach a target depth = C × G; dividing by read length gives the read count.

Model assumptions and when they break down:

Lander-Waterman assumes reads are uniformly and randomly distributed across the genome. In practice this assumption frequently fails:

• GC bias: regions with very high or very low GC content have significantly lower coverage;
• Repetitive sequences: reads in multi-copy regions cannot be uniquely mapped, so effective depth falls below the mean;
• Capture sequencing: exome and panel assays typically achieve only 60–80% on-target rates. This discount must be factored in when calculating data volume, or actual depth will fall well short of the target.

The values calculated here represent theoretical mean depth. Real uniformity must be assessed from the post-alignment coverage distribution, not from this average.