What is Stock & Flow?

Stock & Flow is a free browser-based pipeline simulator that helps you model multi-stage systems like supply chains, hiring funnels, onboarding pipelines, and manufacturing processes. It automatically identifies bottlenecks, forecasts throughput, and shows how interventions shift constraints over time.

How does pipeline bottleneck analysis work?

Stock & Flow uses system dynamics simulation with Erlang delay chains to model how items flow through pipeline stages. Each stage has capacity, transit time, and conversion rate parameters. The simulator runs daily ticks with backpressure propagation, then analyzes utilization and stock levels to identify which stage is the binding constraint limiting overall throughput.

What types of pipelines can I model?

Any multi-stage process where items flow through sequential stages with capacity constraints. Common examples include: supply chain and logistics pipelines, hiring and recruitment funnels, customer onboarding flows, manufacturing and production lines, SaaS conversion funnels, patient care pathways, and order fulfillment systems.

Is Stock & Flow free?

Yes. Stock & Flow is completely free. It runs entirely in your browser with no account required. Your data is stored in your browser's local storage and never sent to any server.

What is the Theory of Constraints and how does Stock & Flow use it?

The Theory of Constraints (TOC), developed by Eliyahu Goldratt, states that every system has a single binding constraint that limits its throughput. Stock & Flow automatically identifies this constraint by simulating your pipeline and analyzing which stage has the highest utilization or is hitting its capacity ceiling. It then shows how interventions (like adding capacity or reducing transit time) shift the constraint to the next bottleneck.

How do I share my pipeline model with others?

You can export your pipeline model as a JSON file for backup or sharing. Others can import the JSON file into their own browser to see your exact pipeline configuration.

Stock & Flow — Pipeline Simulator

Stock & Flow is a free, browser-based pipeline simulator for modeling multi-stage systems and finding bottlenecks.

What it does

Model any multi-stage pipeline: supply chains, hiring funnels, onboarding flows, manufacturing lines
Automatically detect the bottleneck limiting your system's throughput
Forecast how stock levels, flow rates, and output evolve over time
Plan interventions and see how they shift bottlenecks and improve results
Get interactive charts and projection tables

How it works

Define your pipeline stages with capacity, transit time, and conversion rates. Stock & Flow runs a system dynamics simulation using Erlang delay chains with backpressure propagation, then identifies the bottleneck and generates a plain-English headline explaining what's limiting throughput and what to do about it.

Use cases

Supply chain & logistics — Model warehouse-to-delivery pipelines, find shipping bottlenecks
Hiring & recruitment — Track candidates through sourcing, screening, interviews, offers
Customer onboarding — Identify where new customers get stuck
Manufacturing — Balance production line stages, plan capacity expansions
SaaS funnels — Model trial-to-paid conversion with realistic delay distributions
Healthcare operations — Patient flow through intake, treatment, discharge

Features

Erlang-3 delay chain simulation for realistic transit time distributions
Backpressure propagation when downstream stages hit capacity
Five interactive visualizations: pipeline snapshot, stock trajectories, throughput vs. capacity, cumulative output, projection table
Initiative planning: model date-triggered changes to capacity, transit time, or conversion rates
Multiple saved pipelines
JSON export and import
Completely free, no account required, data stays in your browser

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Pipeline Simulation Results