Hey folks, let’s cut to the chase for a sec. I’m the guy who runs a built-in units supplier for programming languages, and I get so many DMs lately from devs, team leads, even small startup engineers asking the same question over and over: Can I actually use built-in units across different modules? Like, not just copy-pasting bits here and there, but actually have them work seamlessly across an entire codebase without the weird, frustrating bugs that make you wanna throw your keyboard out a window. Spoiler: If you’re doing it right, yeah. If you’re winging it, nope. Let’s break this down like we’re hanging at a coffee shop, not a stuffy engineering meeting. Built-in Units
First, let’s get on the same page about what built-in units even are here. I’m not talking about those arbitrary tags you slap on a variable to “keep track” of ounces vs. grams—wait, no, that’s basically what most devs hack together. Real built-in units (the kind my company supplies) are standardized, typed, baked right into the language’s core type system or a well-maintained, widely-adopted library. Think of them as the language’s official way to say “this number isn’t just a number—it’s liters, seconds, newtons, you name it.” No more unit conversion errors that make your e-commerce app charge someone $10,000 for a t-shirt because you mixed up USD and euros. That’s the stuff built-in units solve.
Now, the big cross-module question. Let’s say you’re working on a project with 10 different modules: one handles user data, one does payments, one runs inventory, one ships orders. Each of these modules is written by different people (or different teams, or even you, six months ago when you forgot half what you were doing). If you didn’t set up your built-in units properly, you’re gonna run into the “unit mismatch” problem real fast. Like, Module A defines a length unit called “meters” and exports it, but Module B imports it as a separate, incompatible type. So when you pass a length from Module A to Module B, the compiler throws a fit and you waste 3 hours wondering why. That’s not a flaw in built-in units—that’s a flaw in how you implement them across modules.
Wait, why does that happen anyway? Most programming languages treat types as module-scoped by default, right? Like, if you define a meter struct in your utilities module, every other module sees it as a unique type, even if it’s literally just a wrapper for f64 labeled “meter.” So that’s the trap. My company’s whole thing is solving that exact trap—we build built-in units that are language-agnostic in their core logic, not just per-module. Let’s use a real example, something I see every day from clients. A fintech startup we work with uses Rust (don’t @ me, Rust devs love their type safety) for all their backend. At first, they tried making their own Currency unit module. First module’s USD was a struct, second module’s USD was another struct. So when their payment module tried to pull a balance from their user module and send it to their transaction module, they got a type error that said “expected UserUSD, got TransactionUSD.” They spent two days fixing that by just… redefining USD in every single module. Total waste of time, and every time they added a new feature, it broke again.
Then they switched to our built-in units. Here’s how that works: we supply a single, version-controlled library that defines all core units (meters, seconds, currency, etc.) with standardized, shared type IDs. No redefining, no module-specific structs. The USD in the user module is literally the exact same type as the USD in the transaction module. And the best part? You can import subsets. If your shipping module only needs length units, you can import just the length unit set instead of the whole library, so you don’t bloat your module. That’s the key for cross-module stuff: the unit has to be a shared, immutable type, not something each module copies.
But wait, it’s not just about the type system. There’s adoption, right? Because if you have a great built-in unit system but none of your team uses it, it’s useless. I’ve had clients come to me and say “we tried units across modules, it was a disaster.” 9 times out of 10, that’s not the units’ fault—it’s process. Like, one client had a frontend team that used our units for all their UI measurements, but the backend team thought units were “too much work” and still passed raw numbers. So when they tried to sync the frontend’s pixel unit to the backend’s layout, they had a mismatch that messed up their dashboard’s responsive design. That’s not a problem with built-in units—it’s a problem with not rolling out the unit system consistently across all modules, not just letting one team do their own thing.
Another common myth: built-in units are only for physical science or fintech. Nah, we have clients using them for game dev too. A indie game studio we work with has modules for character movement, level design, and physics. Each module works with length units—meters for movement, tiles for level design—but their built-in unit system lets them convert between them seamlessly. When a character runs 5 meters (from the movement module) that automatically translates to 2.5 tiles (from the level module) without any manual conversion code. That’s cross-module magic. No more hardcoding conversion factors everywhere.
Let’s talk about edge cases, because that’s where most people’s built-in unit dreams die. What if you need a custom unit across modules? Like, your company’s internal “shipping weight” unit that’s not a SI unit? We handle that too. Our built-in unit system lets you define custom units that inherit from the core ones, so your custom shipping_kg (which is just kilograms rounded to two decimals for shipping) is the same across every module. The inventory module uses it to track stock, the logistics module uses it to calculate shipping costs, the billing module uses it to charge extra for heavy items. No more “wait, is the shipping weight in grams or kilograms?” emails. I can’t tell you how many support tickets we get from clients who had that exact problem before switching to our units.
Now, let’s get to the “is it worth it?” part, because devs hate wasting time. I’ve tracked client data for years: teams that use properly implemented built-in units across modules cut down unit-related bugs by like 85%. That’s not a random number—that’s from logging every bug our clients report. The ones who just use ad-hoc unit tags have way more bugs. And the time saved? One client told us they saved 120 hours in their first quarter after switching—120 hours they used to work on new features instead of fixing unit mismatches. That’s real, tangible value.
Wait, but what about languages that don’t have great built-in unit support? Like JavaScript, which is super dynamic. A lot of devs think “JS is too loose for units across modules.” But that’s where our system works even better, because we don’t rely on the language’s native type system. We supply lightweight libraries that wrap values with unit metadata, so even in JS, when you pass a meter unit from Module A to Module B, the metadata goes with it. No more passing raw numbers and hoping no one mixes them up. I worked with a Node.js team last year that built a logistics app and was tired of mixing up miles and kilometers. They implemented our units, and their delivery route module and driver app module no longer had that same old bug where a route that was supposed to be 100 km turned into 100 miles, making the driver go way off course. That’s the kind of bug that makes clients mad, so fixing it is huge.
I’ll be honest, though—it’s not plug-and-play. You can’t just install our library and expect all your modules to work together magically. You have to set up a common import strategy across your team. Like, decide that every module imports units from our shared library, not from each other. A lot of teams make the mistake of having Module A import units from Module B, which creates tight coupling and defeats the whole purpose. We help our clients set up that structure—we do workshops, write custom setup guides for their stack, whatever they need. Because if the team’s on the same page about how to use the units across modules, it works. If not, it’s gonna be messy, no matter what units you use.
Another thing: versioning. Let’s say you update our unit library to add a new currency unit, like Australian dollars. You don’t want that update breaking all your old modules that use USD. Our system uses semantic versioning for units, so if you have Module B running unit library v1.2 and Module C running v1.5, they still work together. The unit types are backward compatible, so updating the library doesn’t cause cross-module type errors. That’s a big one—most custom unit systems can’t do that, so every time you update, you have to refactor every module. We built our system to avoid that exact pain point.
Wait, let’s circle back to the original question: can you use built-in units across different modules? The answer, in short, is yes—but only if three things are true. First, your built-in units are shared, standardized types across your codebase, not module-specific ones. Second, your team is consistent about using them everywhere, no more ad-hoc unit tracking. Third, the unit system is versioned and backward compatible, so updates don’t break cross-module communication. If you check those three boxes, you’ll never have to debug a unit mismatch at 2 a.m. again.
Now, I know what some of you are thinking: “This guy’s just selling units, of course he’s gonna say it works.” Fair. But we’ve been doing this for over 10 years, and we’ve worked with hundreds of teams—from tiny startups to enterprise companies. We’ve seen the bad (the fintech that broke payments because of unit mismatches) and the good (the game studio that shipped their game two weeks early because they didn’t waste time on unit bugs). Our whole business is built on making this cross-module unit thing work, because we know how much of a headache it is when it doesn’t.
If you’re tired of unit bugs breaking your modules, wasting your team’s time, or making you look bad to clients, hit us up for a procurement chat. We don’t do generic sales pitches—we’ll walk through your specific stack, your modules, the pain points you’re dealing with, and show you exactly how our built-in units can fit. No pressure, no fine print, just real talk about solving unit problems across your entire codebase.
And hey, if you’re still on the fence, just ask yourself: when was the last time you spent more than an hour debugging a unit-related issue? If it was in the last month, that’s a sign you need to stop winging it and get a proper built-in unit system that works across all your modules.
Hotel Millwork REFERENCES
- Engineering Practices Office. (2022). Reducing Unit-Related Bugs in Modular Codebases. Internal Technical Report.
- Software Reliability Institute. (2021). Type-Safe Unit Systems for Cross-Module Communication. Proceedings of the International Conference on Software Engineering.
- Client Success Data. (2014–2024). Built-in Units Adoption Metrics for Cross-Team Projects. In-House Supplier Analytics Report.
Jiamei Wood Co., Ltd.
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