Contact person: Business Client

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Location: Coventry, United Kingdom

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"I need a fully-functional BTU calculator added to my OpenCart store so customers shopping for heating systems can quickly see the heat output they require.

The calculator must:
• Appear seamlessly on relevant product and landing pages.
• Ask for Room size, Insulation type, Window Type, Region in the UK and any Additional Factors I add later through the admin.
• Return a single, clear Recommended BTU value as soon as the form is completed.

Please build the front-end widget in responsive HTML / CSS with lightweight JavaScript or jQuery for instant calculations, and code the back-end in PHP so I can adjust coefficients and labels inside the OpenCart admin (v3.x). The calculation logic should be cleanly separated, well-commented and easy for me to tweak.

Acceptance criteria
1. All fields validate gracefully and work on mobile and desktop.
2. Recommended BTU value updates instantly without page reload.
3. Admin settings let me modify factors, wording and multipliers.
4. No core files overwritten; extension installs via OCMOD or VQMod and runs error-free on my staging and live sites.

If you’ve built similar OpenCart calculators or modules, a quick demo or code sample will help me choose faster." (client-provided description)