Do I need to install anything?

No. It runs in any modern browser, free, with no account required.

For Hobbyists & Makers · Inventory & Demand

Inventory & Demand for a GDP forecast

Built for hobbyists & makers exploring it for fun. Play with real physics and math, no license and no setup — just open and tinker. Simulate a GDP forecast live below — adjust the inputs and watch it respond, right in your browser.

Eoq

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Economic Order QuantityLive

the inventory sweet spot

Controls

Presets

Annual demand D

Cost per order S ($)

Holding cost H ($/unit/yr)

Order too often and ordering costs pile up; order too much and holding costs balloon. The Economic Order Quantity, EOQ = √(2DS/H), is the order size that minimizes their sum. At the optimum the ordering and holding costs are exactly equal — the crossing point of the two curves. The foundation of inventory management.

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Data Inspector

EOQ707 units

Orders / year14.1

Min total cost$1414

Governing equation

Q^{*} = \frac{2 D S}{H} = \frac{2 \cdot 10000 \cdot 50}{2} = 707

Reading this result: At the EOQ the two curves cross: yearly ordering cost equals yearly holding cost, giving about 14.1 orders a year at the minimum total cost.

Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.

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Monte Carlo

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Monte Carlo Price SimulationLive

geometric Brownian motion

Controls

Presets

Initial price S₀

Expected return μ

Volatility σ

Horizon (years)

Geometric Brownian motion models a price with constant drift and random volatility — the assumption behind Black-Scholes. Running hundreds of simulated paths reveals the full distribution of outcomes, not just an average. Educational tool, not investment advice.

▶ Run in Python

Data Inspector

Median outcome$0

5th percentile$0

95th percentile$0

Governing equation

S_{t + Δ t} = S_{t} e^{(0.07 - \frac{0. 2 ^{2}}{2}) Δ t + 0.2 Δ t Z}, \tilde{S}_{1} \approx $0

Reading this result: Median outcome is about $0, just under the drift-only $107 — GBM compounds in log-space, so volatility always pulls the typical path below the average.

Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.

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Frequently asked questions

Is this good for hobbyists & makers?: Yes — this version of "Inventory & Demand for a GDP forecast" is framed for hobbyists & makers exploring it for fun. Play with real physics and math, no license and no setup — just open and tinker.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.