SolidWorks plugin budgets in the UK run from about £1,100 for a small macro to well over £100,000 for a commercial product sold to other engineering firms. That spread is why the first quote you receive can feel arbitrary. The price is not arbitrary, though. It follows from three things you can pin down before anyone writes code: what kind of plugin you need, how many days of skilled C# work it takes, and how many SolidWorks releases it has to survive.
This guide puts sterling numbers on each of those. It uses published UK contractor rates from the six months to 4 October 2026, the current UK SolidWorks price list, Dassault Systèmes’ own API documentation and a fully worked example with the arithmetic shown. Where a figure is our planning assumption rather than a published rate, it is labelled as one.
A note on words: Dassault’s documentation calls these extensions “add-ins”, while most buyers search for a SolidWorks plugin. They are the same thing, and this guide uses both terms. If you are weighing a plugin as part of wider CAD automation, our earlier piece on how software is improving CAD automation covers the bigger picture.
Table of contents
- What Counts as a SolidWorks Plugin?
- SolidWorks Plugin Cost by Complexity Tier
- The Day Rates Behind Every SolidWorks Plugin Quote
- Seven Factors That Push SolidWorks Plugin Development Cost Up
- Licences and Tools a SolidWorks Plugin Needs
- Worked Example: Pricing a Mid-Size SolidWorks Plugin
- The Yearly Cost of Keeping a SolidWorks Plugin Working
- In-House, Freelancer or Agency: Who Should Build It?
- Six Ways to Cut SolidWorks Plugin Development Cost
- Does a SolidWorks Plugin Pay for Itself?
- SolidWorks Plugin Cost FAQs
- References
What Counts as a SolidWorks Plugin?
The type of SolidWorks plugin you need sets the price floor before scope is even discussed. SolidWorks exposes its API in several ways, and each one carries a different build cost, a different deployment model and a different maintenance burden.
Macros: the cheapest starting point
A VBA macro (a .swp file) runs inside SolidWorks and can often be recorded first, then tidied by hand. Macros are ideal for one repetitive task, such as saving every drawing in a folder as PDF. They are also fragile: they live on individual PCs, have no installer, and are hard to version or support once three people have edited them.
Add-ins: the standard SolidWorks plugin
A true add-in is a compiled C# or VB.NET library that SolidWorks loads at start-up. According to the SolidWorks API help, the add-in implements the ISwAddin interface, whose ConnectToSW and DisconnectFromSW methods are its entry and exit points, and it registers its class ID under the SolidWorks AddIns registry key. This is the same in-process COM model that Office used for the add-ins we compared in our guide to VSTO add-ins versus Office add-ins.
Standalone tools, PDM add-ins and Document Manager apps
Three other shapes are worth knowing. A standalone program can drive SolidWorks from outside for overnight batch jobs. A PDM Professional add-in runs inside the vault client and reacts to workflow events. A Document Manager application reads and writes file properties and BOM data without SolidWorks running at all, but needs a licence key from Dassault.
| Plugin type | Where it runs | Best for | Relative cost |
|---|---|---|---|
| VBA macro | Inside SolidWorks, per PC | One repetitive task | Lowest |
| C# add-in | Inside SolidWorks, loaded at start-up | Menus, task panes, design rules | Medium to high |
| Standalone program | Outside, driving SolidWorks | Overnight batch jobs | Medium |
| PDM Professional add-in | Inside the vault client | Workflow and approval logic | Medium to high |
| Document Manager tool | Anywhere, no SolidWorks needed | Reading properties and BOMs at scale | Low to medium |
SolidWorks Plugin Cost by Complexity Tier
Most SolidWorks plugin projects fall into one of five tiers. The day counts below are our planning ranges from scoping this kind of work. The prices are those day counts multiplied by £550, the UK median C# developer contract rate in the six months to 4 October 2026 (ITJobsWatch).
| Tier | Typical scope | Effort | Cost at £550/day |
|---|---|---|---|
| 1. Macro | One task, such as batch PDF export | 2–5 days | £1,100–£2,750 |
| 2. Simple add-in | Toolbar commands, property editor, batch export | 10–20 days | £5,500–£11,000 |
| 3. Mid-size add-in | Task pane, PropertyManager pages, rules, a database link | 30–60 days | £16,500–£33,000 |
| 4. Complex add-in | Design automation, configurators, PDM and ERP sync | 80–150 days | £44,000–£82,500 |
| 5. Commercial product | Multi-version support, licensing, installer, support desk | 150–300 days | £82,500–£165,000 |
Tier 1 and 2: macros and simple add-ins
A macro that exports drawings or renames files is a few days of work. Moving the same logic into a simple SolidWorks plugin with its own toolbar, error handling and an installer roughly triples the effort, because the code now has to behave on every PC rather than one.
Tier 3: the mid-size SolidWorks plugin
This is where most engineering firms land. A task pane that writes custom properties, checks naming rules and saves outputs to a network share is a typical mid-size SolidWorks plugin. The worked example later in this guide sits at the bottom of this tier.
Tier 4 and 5: automation and products
Design automation, where the plugin builds or reconfigures models from rules, is the most expensive category because every geometry edge case must be handled. A commercial product adds licensing, documentation, a support process and testing across several SolidWorks releases at once.
The chart below shows the midpoint of each tier at the same £550 day rate, so the jump between tiers is easy to see.
The Day Rates Behind Every SolidWorks Plugin Quote
Almost all of a SolidWorks plugin budget is developer time, so the day rate matters as much as the scope. ITJobsWatch tracks advertised UK contract rates, and its figures for the six months to 4 October 2026 give a useful range.
What UK contractors charge
The median C# developer contract rate was £550 a day across 137 quoted rates, with the 25th percentile at £463 and the 75th at £713. Outside London the median was £485. Senior C# developers had a median of £600, while C++ developers, needed for some low-level SolidWorks API work, commanded a median of £819.
Why “SolidWorks” job ads look cheaper
Contract ads that mention SolidWorks had a median of £438 a day, but only 20 rates were quoted and most of those roles are CAD design jobs, not API development. Do not use that figure to budget a SolidWorks plugin. The person you need is a .NET developer who knows the SolidWorks API, and they price like one.
The chart applies each published rate to the same 36-day project used in the worked example below.
Agency and in-house rates
Agencies usually charge more per day than individual contractors, typically £550–£750 in our planning range, because the rate covers project management, testing and cover when a developer is away. An in-house hire costs less per day on paper, but ITJobsWatch puts the median permanent salary for SolidWorks roles at £50,000, before employer costs, a dedicated SolidWorks seat and the months it takes to learn the API.
Seven Factors That Push SolidWorks Plugin Development Cost Up
Two plugins with the same one-line description can differ in price by a factor of three. These are the factors that explain the gap, roughly in order of impact.
1. How much the plugin touches geometry
Reading and writing custom properties is cheap. Creating features, editing sketches or rebuilding configurations is not, because every model in your library has quirks the code must survive. A SolidWorks plugin that edits geometry needs far more testing against real customer files.
2. User interface depth
A single toolbar button is quick. A task pane with forms, validation and live previews, or native PropertyManager pages that behave like built-in SolidWorks commands, can add two to three weeks on its own.
3. The number of SolidWorks versions supported
If every seat in your company runs the same release, you test once. If suppliers or customers run older versions, each extra release adds test cycles and sometimes version-specific code paths.
4. Integrations
Pushing a bill of materials into ERP, reading part numbers from a database or reacting to PDM workflow states each adds its own design, error handling and test effort. Integrations are where estimates most often slip.
5. Large assembly performance
Code that works on a ten-part assembly can grind on a 5,000-part one. Making a SolidWorks plugin fast on large assemblies, for example by working with lightweight components or the Document Manager API, takes deliberate engineering time.
6. Data quality in your existing models
If file names, custom properties and templates are inconsistent, the plugin must cope with every variation or you must clean the data first. Either way, someone pays for it.
7. Who owns the specification
A clear, signed-off specification is the cheapest risk control available. When requirements are discovered during the build, the same SolidWorks plugin can easily cost 30 to 50 percent more than its first estimate.
Licences and Tools a SolidWorks Plugin Needs
Developer time dominates, but a SolidWorks plugin also needs software around it. Some of these costs are one-off, some recur every year, and a few are free if you know where to look.
SolidWorks seats for development and testing
The developer needs a licensed copy of SolidWorks to build and test against. The UK price list published in August 2026 gives annual subscriptions, excluding VAT, of £2,544 for SolidWorks Design Standard, £3,156 for Professional and £3,876 for Premium. Many clients let an external developer use one of their existing seats during the project, which removes this cost.
The Document Manager licence key
The Document Manager API needs a licence key requested through the SolidWorks customer portal. Dassault’s documentation says keys are only issued to customers whose serial number is on subscription, and a new key is needed for each new major release. The key itself carries no extra charge, but the subscription requirement does.
Visual Studio and frameworks
Visual Studio Community is free for individuals and small organisations, but Microsoft’s licence defines an enterprise as any organisation with more than 250 PCs or users or more than one million US dollars in annual revenue, and those firms need a paid edition for commercial work. Open-source frameworks such as xCAD.NET, released under the MIT licence, can remove weeks of boilerplate.
Code signing
An unsigned installer triggers Windows warnings, and many IT and cybersecurity teams will block it outright. Microsoft’s Artifact Signing service starts at $9.99 a month for 5,000 signatures and is open to organisations in the UK with at least three years of verifiable tax history. Microsoft’s code signing guide lists traditional OV certificates at roughly $150–$300 a year.
| Item | Typical cost | When you pay |
|---|---|---|
| SolidWorks Design Standard seat | £2,544 a year, ex VAT | Yearly, unless the client lends a seat |
| Document Manager API key | No charge, subscription required | Re-requested each major release |
| Visual Studio Community | Free for non-enterprise users | Paid edition above the enterprise threshold |
| Artifact Signing, Basic | $9.99 a month | Monthly |
| OV code signing certificate | $150–$300 a year | Yearly |
| Solution Partner Program extra licence | $100 processing fee each | Per additional licence |
Selling your SolidWorks plugin to others
If you plan to sell the plugin, the SolidWorks Solution Partner Program has three levels: Research Associate, Certified Solution Partner and Certified Gold Partner. Its FAQ has stated that an accepted Research Associate receives one free partner licence of SolidWorks, with a $100 processing fee for each additional licence or upgrade, so confirm the current terms with the partner team before you budget.
Worked Example: Pricing a Mid-Size SolidWorks Plugin
Here is a realistic brief. A UK manufacturer with 40 SolidWorks seats wants one plugin that fills in custom properties from a task pane, exports PDF drawings and DXF flat patterns for sheet metal parts, and writes the bill of materials to a file their ERP system imports. Everyone runs the same release, and a second release must be supported for one year during the upgrade.
The effort, phase by phase
| Phase | Days | Cost at £550 | Share |
|---|---|---|---|
| Discovery and specification | 3 | £1,650 | 8.3% |
| Architecture and task pane design | 3 | £1,650 | 8.3% |
| Core build: properties and export engine | 14 | £7,700 | 38.9% |
| ERP bill of materials output | 5 | £2,750 | 13.9% |
| Testing on two releases with real models | 6 | £3,300 | 16.7% |
| Installer, signing and roll-out | 2 | £1,100 | 5.6% |
| Documentation, training and handover | 3 | £1,650 | 8.3% |
| Total | 36 | £19,800 | 100% |
Adding contingency
We add 15% contingency to a fixed scope like this one: £19,800 × 0.15 = £2,970, giving a budget of £22,770. Note that the core build is under 40% of the total. Testing, integration and handover together take more days than the core build, which is why a quote that is mostly “development” is usually missing something.
What changes the number
If the client also wanted the plugin to build sheet metal parts from a rules table, the job would move into tier 4 and roughly triple. If they dropped the ERP output and the second release, it would fall to around 28 days, about £15,400 at the same rate.
The Yearly Cost of Keeping a SolidWorks Plugin Working
The build is not the last bill. Dassault Systèmes ships a new SolidWorks release every year, followed by a run of service packs, and every one is a chance for a SolidWorks plugin to break.
The annual release cycle
At the time of writing, SolidWorks 2026 had reached Service Pack 4.1, released on 14 September 2026, and Dassault had opened the SolidWorks 2027 preview programme to customers on 15 July 2026. A plugin needs at least a regression test on each major release, and sometimes code changes when the API or the user interface moves.
The .NET runtime trap
Most add-ins have traditionally targeted .NET Framework 4.x. Modern .NET can be used through COM hosting, but Microsoft’s documentation states that only one modern .NET runtime can be loaded inside a single process. If another vendor’s add-in has already loaded an incompatible runtime, your plugin can fail to load. That is a support cost you choose at design time.
A realistic maintenance budget
For the worked example we budget 4 days a year for release testing and fixes, plus 4 days for small improvements: 8 × £550 = £4,400 a year. That is 19.3% of the £22,770 build, in line with the 15–25% a year we use for custom software. If you already run older macros nobody understands, our guide to legacy software modernisation cost explains how to price replacing them.
The takeaway before the chart: over three years, upkeep adds about 39% to the build price.
In-House, Freelancer or Agency: Who Should Build It?
The same scope costs different amounts depending on who delivers it, and the cheapest day rate is not always the cheapest outcome.
| Option | Cost basis | Strength | Main risk |
|---|---|---|---|
| In-house developer | £50,000 median salary plus on-costs | Knows your products and data | Learning curve; single point of failure |
| Freelance contractor | £463–£713 a day | Low overhead, fast start | No cover; code ownership must be agreed |
| Specialist agency | £550–£750 a day (planning range) | Team cover, testing, project management | Higher day rate |
When in-house makes sense
If you will build several SolidWorks plugin projects a year, a permanent developer pays off. Budget for the learning period: the SolidWorks API is large, and a strong C# developer new to it is rarely productive in the first month.
When to bring in outside help
For one plugin, or for a first project that proves the idea, a contractor or agency is usually cheaper overall. The questions to ask are similar to those in our guide to hiring add-in developers: ask for examples of API work, who owns the source code, and how the supplier tests against new releases.
Six Ways to Cut SolidWorks Plugin Development Cost
You can bring a SolidWorks plugin budget down without accepting a fragile result. These six habits save the most money on the projects we see.
1. Prototype with a macro first
A two-day macro proves whether the idea saves time before you commit £20,000 to a full add-in. If engineers do not use the macro, they will not use the plugin either.
2. Pay for discovery separately
A short, fixed-price discovery phase produces a specification you can get quoted by anyone. Our comparison of fixed-price and time-and-materials contracts explains when each model protects you.
3. Support one release where you can
Agreeing that every seat upgrades together can cut testing effort substantially. Each extra SolidWorks release supported multiplies test cycles.
4. Use proven frameworks
Frameworks such as xCAD.NET already handle add-in registration, commands and property pages. Paying a developer to rebuild that plumbing is money that does not reach your users.
5. Clean your data before automating it
Fixing templates and custom property names first makes the code simpler and the SolidWorks plugin more reliable. It also helps every engineer, plugin or not.
6. Own the source code
Make sure the contract gives you the source code and build instructions. Without them, the next SolidWorks release can turn a small fix into a rewrite.
Does a SolidWorks Plugin Pay for Itself?
Cost only matters next to the time saved. Here is a simple payback test using the worked example; the time saving and working hours are assumptions, so substitute your own.
The payback arithmetic
Take 8 designers who each save 20 minutes a day on 220 working days: 8 × 20 ÷ 60 × 220 = 587 hours a year. Using the £50,000 median SolidWorks salary over 1,650 working hours gives £30.30 an hour, or £39.39 with 30% employer costs. That puts the time saved at about £23,111 a year.
What the result means
Against a £22,770 build, the plugin pays back in just under 12 months, and from year two it returns about £18,700 a year after the £4,400 maintenance budget. If the saving were only 5 minutes a day, payback would stretch to almost four years, which is why measuring the current manual process comes first.
SolidWorks Plugin Cost FAQs
How much does a simple SolidWorks plugin cost?
A simple add-in with a few toolbar commands, such as batch export or a custom property editor, typically takes 10–20 days. At the £550 UK median contract rate that is £5,500–£11,000, before any SolidWorks licence costs.
Is a macro or an add-in better?
A macro is cheaper and fine for one person and one task. An add-in is better when many people use the tool, when it needs a proper interface, or when it must be installed, updated and supported centrally.
Do I need to buy SolidWorks for the developer?
Not always. Many firms let an external developer use an existing seat during the project. An in-house developer needs a dedicated seat, which starts at £2,544 a year for SolidWorks Design Standard.
Will my plugin work in the next SolidWorks release?
Usually, but it must be tested. The API is largely backward compatible, yet each yearly release can change behaviour, and Document Manager keys must be renewed for every major release.
How long does it take to build a SolidWorks plugin?
In our experience, elapsed time is one and a half to two times the effort in days, because of reviews and testing with real users. The 36-day worked example would typically take two and a half to three and a half months from kick-off to roll-out.
Can you build a SolidWorks plugin in Python?
Python can automate SolidWorks through its COM interface from outside the program, which suits batch scripts. A true in-process add-in is normally written in C# or VB.NET, and that is what most UK developers will quote for.
Whatever tier you land in, the cheapest SolidWorks plugin is the one specified clearly before the build starts. If you want a second opinion on a quote or a scope, our software development team can help.
References
SOLIDWORKS API Help: ISwAddin Interface
SOLIDWORKS Document Manager API: Getting Started
SOLIDWORKS 2027 Preview Is Live!
SOLIDWORKS Technical Alerts and News
SOLIDWORKS Solution Partner Program Levels
ITJobsWatch: C# Developer Contract Rates
ITJobsWatch: SOLIDWORKS Permanent Salaries
Microsoft Learn: Code Signing Options for Windows App Developers
