# Phage Burst Size Calculator (One-Step Growth)

Compute phage burst size = (PFU after lysis − PFU input) / infected cells from a one-step growth experiment, with Poisson MOI guidance and typical-range interpretation.

> Canonical page: https://elysiatools.com/en/tools/phage-burst-size

- **Category:** Health

- **Keywords:** phage burst size, bacteriophage, one-step growth, lysis, pfu, phage titer, virology, moi, multiplicity of infection, phage propagation, lysate, lab calculator

## Overview

The Phage Burst Size Calculator computes average progeny per infected cell from a one-step growth experiment. Enter free phage titer after lysis, phage input at infection, host cell density, and infected-cell percentage to get burst size, net progeny, and a typical-range interpretation.

## Inputs

- **Free phage titer after lysis (PFU/mL)** (number): Free phage in the lysate at the end of the one-step growth curve.
- **Phage input titer at infection (PFU/mL)** (number): Phage added at the start of infection (0 is acceptable when negligible).
- **Cell density at infection (cells/mL)** (number): Host cell density when phage was added (e.g. mid-log ~1×10⁸ cells/mL).
- **Infected cells (%)** (number): Infected fraction in %. From MOI via Poisson: 1 ≈ 63%, 2 ≈ 86%, 3 ≈ 95%, 5 ≈ 99%.
- **Decimal places** (number)

## When to use

- After a one-step growth curve when you have post-lysis PFU/mL, input PFU/mL, and host density at infection.
- When converting MOI into an infected-cell percentage with Poisson adsorption before reporting burst size.
- When comparing isolates or conditions using burst size (PFU per infected cell) rather than raw lysate titer.

## How it works

- Enter free phage titer after lysis (PFU/mL) and phage input titer at infection (PFU/mL; 0 is allowed if input is negligible).
- Enter cell density at infection (cells/mL) and infected cells in percent (Poisson guide: MOI 1 ≈ 63%, 2 ≈ 86%, 3 ≈ 95%, 5 ≈ 99%).
- Optionally set decimal places (0–6; default 1).
- The tool calculates net progeny, infected cells, burst size = net PFU ÷ infected cells, and a range note (low, common, high/T4-like, or check if very high).

## Use cases

- Report burst size from a one-step growth experiment on a new bacteriophage isolate.
- Compare hosts, temperatures, or MOI by converting titers into PFU per infected cell.
- Apply Poisson MOI guidance so infected-cell counts match the actual adsorbed fraction.

## Frequently asked questions

### What formula is used for burst size?

Burst size = (PFU after lysis − PFU inoculated) ÷ infected cells. Infected cells = cell density × (infected % ÷ 100).

### How do I choose infected cells (%) from MOI?

Use Poisson adsorption P = 1 − e^(−MOI): MOI 1 ≈ 63%, MOI 2 ≈ 86%, MOI 3 ≈ 95%, MOI 5 ≈ 99%. Enter that percentage.

### Can the phage input titer be zero?

Yes. Use 0 when residual input PFU is negligible compared with the post-lysis titer.

### How is the result interpreted?

<20 is low (small-genome phage or suboptimal infection); 20–100 is common (λ ≈ 50–100); 100–300 is high (T4-like ≈ 100–200+); >300 may be inflated by secondary adsorption and should be checked.

### What units should I enter?

Use PFU/mL for both titers and cells/mL for density so burst size is PFU per infected cell.

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