Pocket Tools › Maxable

What it is

A sidebar for Google Sheets. You tell it three things: the objective cell, the cells it may change, and the constraints. It reads your model by nudging the cells and watching your formulas respond, so there is no formula language to learn and no formula parsing to go wrong: SUM, SUMPRODUCT, plain arithmetic and references across the sheet all work, as long as the model is linear. Then it solves, and writes the optimal values into your cells, so your own formulas recalculate and you read the answer in your own sheet. Your cell values, formulas and results are never sent anywhere. The only request that goes outside is the paid license check, described below.

What it does

• Works on the sheet you already have. Three inputs: the objective cell, the cells to change, and constraints written as ranges. One constraint row such as B7:B8 <= C7:C8 compares a whole range at once; the right side can also be a single number.
• Shows what it is doing while it runs. Variables, cells read, coefficients found so far, elapsed time, and a Stop button that stops at once and leaves your cells as they were.
• Writes the answer into your cells to change, and offers Restore previous values to put the old numbers back if you change your mind. Changes made by an add-on are outside the sheet's own undo, so the button is there instead.
• Says why when it cannot solve. No solution satisfies all constraints, the objective can grow without limit, the model is not linear, or a cell does not depend on the cells to change. It never writes a guess.
• Refuses non-linear models rather than returning a wrong answer. A formula that multiplies or divides two changing cells is reported by name.
• Inserts a sample model on an empty sheet, a small production mix with three products and two resources, so there is something to press Solve on before you have built anything.

How a model looks

Put the quantities to decide in a range, say B2:B4. Write the total you care about as a formula that uses them, say =SUMPRODUCT(B2:B4, C2:C4) for profit. Write each resource use as a formula too, and its limit as a number next to it. Then in the sidebar:

• Objective: B10, Maximize
• Cells to change: B2:B4
• Constraint: B7:B8 <= C7:C8

Press Solve. Reading the model takes a few seconds per handful of variables, because every coefficient is measured from your own formulas; the sidebar tells you the expected time before you start and shows progress while it runs. Leave the sheet alone until it finishes.

What it solves, and what it does not

Linear programs: production mixes, diet and feed blends, budget splits, staff rosters, shipping plans, anything where a fixed resource is shared out for the best total and every relationship is a straight line. It does not do integer or binary variables (a machine that is on or off, a warehouse that is built or not), and it does not do non-linear models. Those it declines and says so, rather than returning an answer that looks right.

Pricing

Free: models up to 5 variables and 5 constraint rows, up to 10 solves a day. Textbook and coursework problems fit inside that with room to spare. Only solves that return an answer count; an error, a stop or a refused model does not.
Paid: an annual license, $39 a year, which removes all three limits. There is no feature difference between free and paid: the paid version is the same solver without the limits.

The price shown is the total you pay. Sales tax and VAT are included in it, not added at the end. Prices are in US dollars.

Buy a license

Checkout is handled by Lemon Squeezy, the seller of record. Your license key arrives by email as soon as the payment goes through. The license renews once a year; you can cancel the renewal at any time from the receipt email, and the key keeps working until the end of the year you paid for.

Refunds. Within 14 days of purchase, write to [email protected] and say what went wrong. No justification beyond that is required. The full wording is in the Terms of Service, section 3.

Activating your key

Your license key is on the confirmation screen right after payment, and in the receipt email. To remove the limits:

1. In Google Sheets, open Extensions › Maxable › Open.
2. Paste the key in the License section of the sidebar and press Activate.

One license covers up to 3 Google accounts. To move it to a different account, press Release this account in the same place, which frees a slot. The license belongs to your account, not to a spreadsheet, so it works in every sheet you open and survives removing and reinstalling the add-on.

The add-on checks the key with Lemon Squeezy at most once every seven days. A single check that cannot reach them switches nothing off: the limits stay lifted for up to 14 days after the last check that did succeed. Past that, the free limits apply until a check gets through again. Solving is not affected either way.

The license check, the one request that leaves

When you enter a license key, the add-on sends the key and an anonymous installation identifier, and nothing else, to Lemon Squeezy, our payment processor, to check that the key is valid. Your spreadsheet is never part of that request. The free version with no key makes no network request at all. Details are in the privacy policy.

Permissions it asks for

• See and manage the current spreadsheet, to read your model, to nudge the cells while it measures the coefficients, and to write the answer. Only the spreadsheet the sidebar is open in; it cannot touch your other files. Reading uses a temporary copy of the sheet inside the same file, which is deleted when the run ends.
• Show a sidebar, the panel itself.
• Connect to an external service, the license check above, and only that.

Support

Something wrong, or a model it reads badly? See the support page.