About PencilSum
PencilSum is a set of free home-project calculators: concrete and roofing for now. They give you the answer first and show the working behind it. I'm Junayd. I build the calculators. I'm not a contractor, so every figure comes from manufacturers, building codes and published price surveys, each with its source and the date I checked it.
Why I built it
Most of what people complain about in online calculators comes down to trust, so that is what PencilSum fixes:
| Common complaint | What PencilSum does |
|---|---|
| You have to give a phone number before you see a price, then the sales calls start | No sign-up, no phone number, no email. The answer is on the page. |
| The estimate is nowhere near the quotes you get, and it has no date | Costs are honest national ranges with the survey and date named, and we say plainly they aren't quotes. |
| Pop-ups and video ads cover the boxes you are typing in | Nothing ever floats over the calculator, and ads stay out of it. |
| You press Calculate, then scroll to find the answer | The answer updates as you type and sits right below your sizes. |
| You get a volume, not what to buy | Bags by size, the extras people forget, and one shopping list for the whole job. |
| You can't tell where the numbers come from | Every page shows how it worked out your answer, and its sources and dates. |
| It breaks on a phone | Built and tested phone-first, on every page, before it goes live. |
How it's made
AI helps me research sources, write the code and draft the text. I check every figure against its source, and the maths is tested by hand. When a source changes (a price survey, a code edition), I update the figure and its checked date. If you spot something wrong, email me and I'll fix it and note the change.
How we make money
The calculators are free. The site earns from ads, and from affiliate links and partner offers that appear only when your result fits them (for example, a bag-price link for a small job). They are always labeled, and they never change the numbers.