Spreadsheet optimisation you can check
Turn spreadsheet decisions into answers you can check.
Paste a spreadsheet model or build one in the grid. Plumline finds the best allocation, then checks it against your own formulas and tells you the status in plain words.
Runs in your browser. No account. Your model stays on your device.
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Spreadsheet model
Products, profit per unit and hour limits, as ordinary formulas.
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Decisions and limits detected
Plumline reads the objective to maximise and the constraints to respect.
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Optimised result
Objective (profit) 1,760
The best allocation within every limit.
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Verification
Optimal solution proven
- Objective checked against your formula
- Every constraint recalculated and satisfied
- ✓ Runs in your browser
- ✓ No account required
- ✓ Your model stays on your device
- ✓ Free to use
- ✓ Five languages
How it works
Three steps to a checked answer
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Paste or build your model
Paste a table from Excel or Google Sheets, or build one in the grid.
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Confirm decisions, limits and objective
Plumline shows the decisions, limits and objective it read, so you can review them before solving.
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Solve and check the result
It finds the best allocation, then rechecks it against your own formulas and reports the status.
Real problems
Decisions people bring to Plumline
From production to budgets, Plumline optimises the everyday decisions people keep in spreadsheets.
Production planning
Choose how much of each product to make for the most profit within your limits.
Featured decisionWorkforce scheduling
Cover every shift with the fewest people while meeting each rule.
More decisions people optimise
- Supplier activation Decide which suppliers to open so demand is met at the lowest total cost.
- Delivery loading Pack orders into vehicles without passing weight or space limits.
- Budget allocation Split a budget across channels for the best return within each cap.
- Project selection Pick the set of projects with the most value that still fits the budget.
How it verifies
Every result shows what was checked
What Plumline understood
Before solving, it shows the objective, decisions and constraints it read from your sheet, so a misread cell surfaces early.
Objective checked again
It substitutes the solution back into your objective formula and confirms the value it reports.
Constraints checked again
It recalculates every constraint from your formulas and confirms the result stays within them.
A clear solve status
It reports whether the answer is optimal, feasible, incomplete, infeasible or unbounded, in plain words.
For eligible continuous models, Plumline estimates how the result may change when a binding constraint is relaxed by one unit. This sensitivity insight is often called a shadow price.
Plumline shows the model it interpreted and rechecks the result against your formulas. It does not claim a whole spreadsheet is correct, and an inaccurate model may not represent the real decision.
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Model interpreted
Plumline shows the decision cells, the objective and the constraints it read.
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Result calculated
It solves the interpreted model and finds the best allocation within every limit.
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Formulas checked
It substitutes the result back into your supported formulas and recalculates each one.
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Status reported
It reports an honest status: optimal, feasible, incomplete, infeasible or unbounded.
Worked examples
Open a real model and solve it
Each one loads a complete model with a known result you can verify yourself.
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Production plan
Maximise profit within available production hours
Open in the solver -
Workforce scheduling
Minimise staff while covering daily demand
Open in the solver -
Project selection
Pick projects to fund under budget and hours
Open in the solver -
Cheapest feed blend
Minimise cost while meeting nutrient minimums
Open in the solver
What it handles
What Plumline can solve now.
Plumline solves linear models where the goal and every limit are weighted sums of your decisions. It supports three variable types (continuous, integer and binary) as well as mixed-integer models that combine them, and it checks the answer against your own numbers whichever you use.
Models you can solve
- Continuous models
- Integer models
- Binary decisions
- Mixed-integer models
Works with your spreadsheet
- Number or formula limits
- Paste from Excel or Google Sheets
- Export the result
Checks built into every result
- Objective checked again
- Constraints checked again
- Solved in your browser
Understand the answer
- See what Plumline understood
- Marginal impact
- Feasible region chart
- Five interface languages
Privacy
Your data stays on your device
The online solver reads and solves your model in the browser. Nothing is uploaded, no account is needed, and closing the tab clears it.
Honest limits
What Plumline does and does not do
It solves linear models
Continuous, integer, binary and mixed models where the objective and constraints are linear.
It fits spreadsheet-sized problems
It is built for the models you keep in a sheet, not for very large industrial instances.
It distinguishes optimal, feasible and incomplete results
It reports whether a result is proven optimal, only feasible, or incomplete, and rejects non-linear terms and strict inequalities rather than guessing.
Google Sheets add-on
It reads the model straight from the sheet you already built, solves it, and writes the answer back so Sheets can check it. Free.
The Google Sheets add-on is currently in review.
Bring a decision you already manage in a spreadsheet
Paste the model yourself, start from an example, or ask for help turning your table into a solvable model.
Questions
Before you try it.
Do I need to install anything?
For the online solver, no. It runs in your browser at plumline.online. A Google Sheets add-on is on the way and will be a free, one-time install from the Workspace Marketplace once it's approved.
How do I write the model?
With ordinary spreadsheet formulas. Put your options in rows, a cell that totals what you care about (the goal), and any limits as rows with an operator and a number. Plumline reads it from there, no special syntax.
What kinds of problems does it solve?
Continuous, integer, binary and mixed-integer linear problems: production, purchasing, blending, staffing, transport, budget allocation, project selection and knapsack-style loading. It does not solve genuinely non-linear ones, such as a quantity multiplied by another quantity, and points you to the cell causing the problem.
Can I set variable types and limits?
Yes. Variable settings lets you mark each decision as continuous, integer or binary (0 or 1) and give it a minimum and maximum. Plumline verifies those limits hold in the final answer and shows the check.
Are my numbers safe?
Yes. The online solver runs entirely in your browser and uploads nothing. The add-on sends no spreadsheet data to Plumline or third parties; its processing takes place within Google's infrastructure under your own account. There is no Plumline account to create and no tracking.
How much does it cost?
The online solver is free. The Google Sheets add-on is planned to be free once it becomes available.
Put a number in front of your next decision.
Free. The online solver runs in your browser and uploads nothing.