The short version. Arch Convert is a free imperial-to-metric converter we built for architects, drafters, and home cooks. It started as a side project to fix a recurring annoyance in our own work, and it's now in daily use at ZGF Architects and Ryder Architecture in Vancouver. This post is the story of how it came together: what was wrong with the tools we were using, who we built it with, and the small set of features that make it different.
Why we built another converter
The honest answer: nobody on our team could find one that handled all the day-to-day work without flipping between tabs.
An architect working in metric on an imperial-spec building has to convert 5' 3 1/2" a dozen times a day. Most online converters make you turn that fractional inch into a decimal in your head before you can type it in, which is exactly where small rounding mistakes start. A drafter doing a quick site-plan check wants to type 120 * 80 in the box and see square meters and acres come back at the same time, not open a separate calculator. And the same person, in the evening, opens a UK recipe and finds out their measuring cup is a different size from the one the recipe was written with.
Three different annoyances, same underlying problem: existing tools weren't designed around how the work actually happens. We thought we could do better by starting from the work, not the math.
How we built it
We're a small team that uses AI tools heavily, which means the slow part of building something like this isn't writing the software, it's figuring out what to make. So from day one we worked alongside real users instead of guessing. Two architecture firms in Vancouver, ZGF Architects and Ryder Architecture, agreed to use early versions on real project work and tell us where the tool got in the way.
The loop was tight. Something a teammate at one of the firms hit on a Tuesday became an updated version they could use Wednesday morning. The tool worked on a phone or a laptop, looked the same in both, and the people using it had strong opinions. That kind of feedback is what turned a generic converter into one with a Units menu, sortable rows, three different kinds of cup, and grams that know the difference between flour and water.
A few specific decisions came directly out of those sessions:
- The Length tab puts feet and fractional inches first, because that's how a North American architect reads a dimension out loud.
- The Area tab can hide rows you don't use, because a metric-only practice doesn't want to scroll past sq ft and acres on every measurement check. The Units menu and sortable rows came from a 20-minute conversation with a project lead at Ryder.
- The Cooking mode treats the cup as three different sizes (US, UK, and metric), instead of quietly picking one. That came from a designer who'd miscalculated a recipe by 17% the previous weekend.
- Grams in the Cooking mode know the ingredient, because flour and water aren't the same weight per cup. A converter that pretends they are is worse than no converter at all.
None of these are clever ideas on their own. They're what comes out of watching real people work and removing the smallest annoyance you can see, then asking what comes next.
The build, in features
The first version was in users' hands within a few days. The full set of features came together over about twelve weeks, but only because we were doing this part-time alongside other client work. The actual cycle, from idea to a version someone could use, was always hours rather than weeks. That's the upside of working with AI tools: the slow part is the decisions, not the typing.
What ended up in the build:
- Feet and fractional inches as input. Type
5' 3 1/2"and the tool understands it directly: 1612.9 mm. Decimal feet, decimal inches, and fractional inches each have their own row, and editing any one updates the others as you type. - Math in any cell. Type
5*2+3, press Enter, and every visible row updates. Useful for quick site arithmetic without opening a separate calculator. - Multiple rows synced. Length, area, and volume each have their own tab, with rows you can sort, hide, or reorder. Your setup sticks the next time you open the tool.
- Three cup sizes. US (236.59 mL), UK (284.13 mL), and metric / Australia / New Zealand (250 mL). All three are visible in the Cooking tab so you can pick the one your recipe uses.
- Grams that know the ingredient. Water, flour, oil, and butter each convert at their real weight per cup, not a single average that's wrong for everything. The choice is right on the row, not buried in a settings menu.
- Pages for individual conversions. /feet-inches-to-mm/, /acres-to-hectares/, /cups-to-ml/, and a few more. Each one has the conversion factor at the top, a short table of common values, and the calculator below.
What we learned from the tools that came before
Every project like this builds on work other people have done first. We used each of the tools below on real projects, and Arch Convert is better for it:
- Inch Calculator for the idea of giving every conversion its own page, which is the structure search engines and AI tools both like.
- RapidTables for leading every page with the formula and a short table of common values.
- ArchToolbox for the reminder that who you're writing for matters more than how many features you have. Speaking to architects in their own language is a real advantage.
- ConvertUnits for the case that having everything in one place matters: don't make people hop between sites for one drawing review.
- Decitectural for the conviction that fractional inches need to be treated as a real input, not an afterthought.
If you need a one-off conversion outside what we cover, any of those five is a good answer.
What's next
We're letting the people who use it decide. If a real annoyance shows up often enough in feedback, we build for it. Updates are small, frequent, and usually ship the same week the request lands. If you want a say in what gets built next, just tell us what you're running into.
Try Arch Convert
The tool is at convert.fluxcotech.com. Free, no signup, no ads. You can save it to your phone or laptop home screen like an app.
If you came here for one specific conversion, the dedicated pages:
- Feet and fractional inches to millimeters
- Square feet to square meters
- Acres to hectares
- Cups to milliliters (US, UK, metric)
- UK gas mark to Celsius
- Imperial to metric, all units
If your practice has a conversion you do every week and we don't cover it yet, tell us about it. We'd rather build for the work you actually do than guess at it.