NeedACalc

NeedACalc · deterministic by design

Build your Calculator with AI

Build a calculator with AI from one plain-language prompt. Test the formula, refine the fields, and share a working calculator—no code required.

Try an example
1 promptStart with a sentence
Generated testsEdge cases included
1 public linkShare instantly
Deterministic runtimeSame inputs, same result

One prompt to a working calculator

A calculator is not just a generated screen

Need a Calc turns your description into editable fields and calculation logic, verifies a working version, then leaves the decision to publish in your hands.

Builder
You describeScale a bread recipe from its original servings to a target batch. Keep each ingredient's unit and reject zero servings.
I’ll create a batch scaler with serving validation, preserved ingredient units, a visible formula, and fixed test examples.

Version 1 completed

Saved
Covered every stated requirement
Built the isolated calculator
Passed model tests
Matched deterministic replays
Passed server verification
Ask to refine anything…
Calculator previewVerified draft

Recipe batch scaler

Base recipe: 4 servings. Adjust the target and the ingredient table recalculates immediately.

Batch multiplier

Units preserved
2.5×
Bread flour750 g
Water450 ml
Yeast7.5 g
Formula

scale = targetServings ÷ originalServings

adjustedAmount = recipeAmount × scale

Build evidenceAll checks passed
Test caseExpected
Same-size batch300 g flour
Double batch600 g flour
Half batch150 g flour
Zero original servingsInput blocked
Ten servings750 g flour
Version 1 · verified draft
Requirement coverage4 / 4
Deterministic replay20 / 20
Server verificationPassed

This version stays private until you review and publish it.

The private preview and published page run the same immutable, verified calculator version.Publish requires your approval

Plain-language rules

Explain the rule in simple terms. AI turns it into a precise calculation.

Live preview

Use real inputs while you build and see each revision immediately.

Visible formula

Review the exact calculation and assumptions before you approve it.

Approved versions

Keep a verified version stable while you continue refining the rule.

Start with the calculation you already understand

How to build a calculator with AI

To build a calculator with AI, describe the rule, verify it with real examples, and publish only the version you are ready to share.

  1. 01

    Describe the inputs and result

    Name the values people will enter, their units, any conditions, and the result they should receive. A rough first sentence is enough to begin.

  2. 02

    Test and refine the logic

    Enter values you know, compare the result with your expectation, inspect the readable formula, and ask for any missing field or rule.

  3. 03

    Approve, publish, and share

    Save the version you checked and share its public link. If the rule changes later, revise it without losing the approved version.

What you get when you build a calculator with AI

A useful calculator with AI should be more than a generated screen. Need a Calc keeps the fields, logic, tests, revisions, and published result connected.

Start from plain language

Describe the job instead of learning a form builder. Need a Calc asks follow-up questions only when a missing detail could change the result.

Calculate while you build

The preview works as soon as a version is ready. Try your own numbers and see each requested change update the calculator beside the conversation.

Get the same result from the same inputs

The approved formula runs consistently in the builder and on the public page. It cannot quietly call an external service or introduce a random value.

Check more than one happy path

Review generated examples for normal values, boundaries, conditions, and invalid input. These checks help expose missing rules before you share the calculator.

Keep a version that already works

Each accepted revision creates a new version. If the latest request changes the logic in the wrong way, return to the previous version.

Share the calculator, not the instructions

Publish one stable link after you approve the result. Other people can enter their own values and calculate without signing in.

FAQ

Questions about building a calculator with AI

What the MVP can build, what you should verify, and what happens after you publish.

Build a calculator with AI from the rule you already use

Describe the inputs and expected result. Need a Calc will turn them into a working preview you can test before you share it.

Start with a sentence