# Cell Confluency Estimator (Microscopy Grid Method) Estimate adherent-cell confluency with the grid-count method: confluency% = occupied/total squares × 100 per field, with multi-field mean ± SD and optional time-to-target from the doubling time. > Canonical page: https://elysiatools.com/en/tools/confluency-estimator - **Category:** Health - **Keywords:** cell confluency, confluency calculator, cell culture, microscopy grid, coverage estimate, passaging cells, doubling time, adherent cells, confluence percentage, cell density, lab calculator, cell biology ## Overview Estimate adherent-cell confluency from microscopy fields with the grid-count method. Enter occupied squares per field and the total squares in the overlay grid to receive mean confluence, standard deviation, range, a growth-stage interpretation, and an optional hours-to-target figure derived from population doubling time. ## Inputs - **Occupied squares per field** (textarea): One occupied-square count per field, separated by commas, spaces, or new lines. - **Total grid squares per field** (number): Total squares in the counting grid overlaid on each field (10×10 = 100). - **Population doubling time (hours, optional)** (number): Leave empty to skip the time-to-target estimate. - **Target confluency (%)** (number): Desired confluency for the time-to-target estimate. ## When to use - When you need a quantitative confluence percentage from grid counts rather than a visual guess. - Before passaging adherent cells to confirm they sit in the typical 70–90% window. - When you know the doubling time and want the remaining hours until a chosen target confluence. ## How it works - Overlay a counting grid on each random microscopy field and count the occupied squares. - Enter one occupied-square number per field together with the total squares per field (commonly 100). - The tool computes confluence % = occupied ÷ total × 100 for every field, then reports the multi-field mean, SD, min–max range and a growth-stage label. - If a doubling time is supplied it also estimates hours to the target confluence with t = doubling time × log₂(target / current mean). ## Use cases - Deciding the optimal moment to passage HEK293, HeLa or other adherent lines. - Recording culture density before transfection, harvest or other timed experiments. - Projecting remaining growth hours from current confluence and a known doubling time. ## Frequently asked questions ### How is confluency calculated? Confluency % equals occupied squares divided by total squares times 100 in each field; the tool then returns the mean, SD and range across the fields you entered. ### How many fields should I count? Count 3–5 random fields per dish to obtain a reliable mean and standard deviation. ### What do the growth-stage labels mean? Sparse (<10%), subconfluent (10–50%), approaching confluence (50–80%), near confluent (80–95%) and fully confluent (≥95%). Routine passaging is usually performed at 70–90%. ### When is the time-to-target estimate shown? Only when you enter a population doubling time in hours; otherwise the estimate is omitted. ### What if I enter only one field? 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