# Human cell sizes ranked by mass: ProteinIQ's analysis

Analysis date: September 27, 2026. This is our descriptive analysis of a published dataset, not new measurements. The question is which human cells are largest and smallest when every cell type is compared on one consistent scale, cell mass, rather than by diameters, volumes, and lengths taken from different studies.

## Findings

The dataset describes 1,264 cell groups, which we combined into 401 cell types. On average, only 10 cell types weigh more than the mature oocyte (1.02 µg): skeletal muscle fibers and nine kinds of long motor, sensory, and descending neurons. The heaviest neuron record, a type Ia/Ib sensory neuron serving the legs, averages 63 µg, about 61 times the oocyte. The oocyte is the heaviest cell type that is neither a muscle fiber nor a neuron. The largest white fat cells (the "large" subcutaneous class, 0.89 µg) approach it.

The lightest entries are platelets (9 pg), sperm (28 pg), and red blood cells (98 pg). Among nucleated body cells, lymphocytes are among the lightest at 0.13 ng. The median nucleated cell in the reference male weighs 0.40 ng, equivalent to a sphere about 9 µm across; the middle half of nucleated cells lies between 0.13 and 0.83 ng (about 6 to 11 µm).

## Input and attribution

Hatton IA, Galbraith ED, Merleau NSC, Miettinen TP, Smith BM, Shander JA. [The human cell count and size distribution](https://doi.org/10.1073/pnas.2303077120). *PNAS* 120(39):e2303077120 (2023). Dataset S01 (`pnas.2303077120.sd01.xlsx`), sheet `Master_Cell_Data`, retrieved September 27, 2026 from the Europe PMC supplementary files for PMC10523466. SHA-256: `6d4ff2b0469c4b11bb222925fbd3a2274bf2336a29230a0a28d66be490cb78b4`. The article is licensed CC BY. We redistribute derived values and cell names, not the original workbook.

## Method

- Each record (`Unique_cell_name`) gives a mean cell mass and cell count for three reference bodies. We used the 70 kg male model where it has a record and the 60 kg female model for female-only cells such as oocytes. Hatton and colleagues treat the male data as primary and derive the others from it.
- For each `Cell_type`, the mean mass is the count-weighted mean of its records: total mass divided by total count. `cell-types-ranked.csv` also lists the heaviest record in each type and the largest upper bound (`Hi_cell_mass_g`).
- The typical cell is the count-weighted median of record masses among nucleated cells in the male model, excluding records whose group is marked non-nucleated (red blood cells, reticulocytes, platelets, and anucleate epithelial cells).
- Equivalent sphere diameters use the paper's conversion density of 1.056 g/mL. They are a size index, not a measured diameter; muscle fibers and neurons are long cylinders.

## Limitations

The masses are mostly estimates from microscope dimensions and assumed shapes, not direct weighings, and the authors note that source values for a cell type can differ up to fourfold. Neuron masses combine the cell body, dendrites, and an axon of assumed length (a median of 84 cm for leg nerves) and diameter; the myelin sheath, which belongs to separate Schwann cells, is excluded. Muscle fiber masses assume that fibers span the length of the muscle belly, which likely overstates long muscles such as sartorius, whose fibers are arranged in series. Fat cell sizes vary with body fat, so the reference male's values will not match every person. Oocyte and sperm masses rest on a few source studies each, and the ranking by type mean hides the spread within broad types.

## Files

- `analyze.py`: reproduction script. `python analyze.py` downloads the supplement, verifies the checksum, and writes the outputs; pass a local workbook path to skip the download. Requires Python 3.10+, pandas, and openpyxl.
- `cell-types-ranked.csv`: 401 cell types ranked by mean mass.
- `selected-cells.csv`: the individual records quoted in the article, with Hatton's source references.
- `summary.json`: headline values, chart values, and ratios.