Yes: the Circle Tools website has free calculators that do not require a sign-in, and the Circle Calculator mobile app is free to download with a useful core that does not require a subscription. Pro is an optional upgrade for people who need selected exports, more advanced workflows, broader workspace limits, or an ad-free experience. This guide separates those three surfaces so that “free” never hides what is optional, platform-dependent, or shown only on the store purchase sheet.
The direct answer: free core, optional Pro
The browser tools on circle.dmrio.com are free to open and use. They do not ask for a Circle account, a payment card, or a subscription before calculating. You can enter a measurement, inspect the formula and result, and leave without creating a profile. That is the clearest meaning of free on this website: the public calculator itself is available without a checkout step.
The Circle Calculator app for iPhone and Android is also free to download. Its core calculations and live diagrams remain usable without starting a Pro subscription. A user who only needs common circle geometry, a quick visual check, or several named workshop results can begin and continue with the free core rather than treating payment as a prerequisite for every useful answer.
Pro is optional. It is intended for people who need selected PDF, CSV, or DXF exports, advanced workflows, wider history, project, or preset capacity, and an ad-free experience. Not every feature belongs to the free tier, so this article names the boundary instead of turning “free to download” into the misleading claim that every tool and export is free.
What the free website includes
The Circle Tools website contains six focused calculators. Each page keeps one geometry job in view, explains the relationship being used, and gives an example that can be checked independently. These browser pages are useful when you need a quick answer on a shared computer, want a linkable formula reference, or do not want to install an app for a single calculation.
The circle tool moves between radius, diameter, circumference, and area. Separate tools cover arc length, sector area and perimeter, chord and segment measurements, annulus or ring area, and bolt-circle PCD coordinates. These are not subscription previews: the browser calculations run on the public pages, and the result is not covered by a purchase dialog.
Free browser access should not be confused with every mobile capability. The website does not promise the app’s saved workspace, every workshop workflow, or professional file export. It offers a defined set of public calculators. Keeping that distinction clear lets you use the website confidently without assuming that a browser result and an app entitlement are the same product surface.
- Circle: radius, diameter, circumference, and area from one known value.
- Arc: solve arc length, radius, or central angle with explicit angle units.
- Sector: calculate area, curved arc, and the ordinary closed perimeter.
- Chord and segment: connect radius, chord, sagitta, angle, arc, and minor-segment area.
- Annulus: calculate ring area, radial width, and inner and outer circumferences.
- Bolt circle: generate evenly spaced PCD hole coordinates and spacing checks.
What you can do in the mobile app without a subscription
The free mobile core begins with the most common job: enter one circle value and obtain radius, diameter, circumference, and area with a diagram that updates alongside the calculation. Ordinary core calculations are not reduced to a static demo screen or a result that disappears behind a paywall.
Named workshop features also have safe free boundaries. Bolt Circle can calculate X and Y drilling coordinates before an optional export is considered. The bundled pipe schedule chart works offline. The metal-weight workflow can return the calculation while an eligible professional PDF remains a Pro addition. These examples show why the accurate statement is “useful free core,” not “everything is free.”
A subscription is not required simply to keep using those free calculations. If you dismiss the Pro offer, the free core remains the free core. If a Pro entitlement later ends, the product is designed to fall back to free access rather than making the basic circle relationship unusable. Keep your source dimensions and job requirements separately, especially for fabrication or safety-critical decisions.
- One-value radius, diameter, circumference, and area calculation.
- Live measurement diagrams that update with the result.
- Core circle and geometry calculations that remain usable without Pro.
- Bolt-circle coordinate results before selected Pro export options.
- Bundled DN/NPS pipe schedule dimensions and weights offline.
- Metal stock weight results before an optional professional PDF workflow.
- Displayed core results that can be checked before considering an export.
Free website, free app core, and Pro compared
The simplest comparison is by job rather than by marketing label. The website handles fast public calculations, the free app core adds mobile diagrams and local continuity, and Pro adds selected professional and workspace conveniences. The exact availability of a specific feature can depend on the current app version and platform, so the live app and store purchase sheet remain authoritative.
| Need | Available without payment | Optional Pro value |
|---|---|---|
| Quick circle answer | Six public web tools and core app calculations | Not required for the basic result |
| Live diagram | Included with core mobile calculations | Not required for the named core diagrams |
| Workshop result | Named free results such as bolt coordinates and metal weight | Selected advanced workflows |
| Files | Read and retain the displayed result | Eligible PDF, CSV, and DXF exports |
| Saved workspace | Defined free history, project, and preset capacity | Expanded capacity for repeat work |
| Advertising | Google Play identifies the Android app as containing ads | Ad-free experience |
This table does not promise that every calculator, workshop mode, or export is free. It deliberately names only the verified core. In particular, professional files and selected advanced workflows belong to Pro, while a browser calculation or named free app result does not require you to subscribe merely to see an answer.
It also does not turn Pro into a requirement for casual use. A student checking a circumference, a maker verifying a PCD layout, or a technician consulting the bundled pipe chart can evaluate the free path first. Upgrade value begins only when the missing export, workspace capacity, advanced workflow, or advertising removal has a practical benefit.
What the optional Pro subscription adds
The optional Pro subscription is a productivity layer, not an entrance fee. Eligible workflows can create professional PDF, CSV, and DXF files so that a result can move into documentation, a spreadsheet, or compatible drawing software. An export carries calculated geometry; it does not add drawing tolerances, machining knowledge, material allowances, or approval for a physical job.
Pro also supports more advanced workflows and broader workspace capacity. Expanded history, active-project, and saved-preset limits matter when the app becomes a repeat-work notebook rather than a one-off calculator. The free limits are intended to remain useful, and an upgrade should solve an observed capacity problem instead of being presented as the only way to save any useful work.
An ad-free experience is another Pro benefit. Google Play currently identifies the Android app as containing ads, so Android users may encounter advertising in the free experience. That platform statement should not be generalized into a claim that every platform displays ads in the same way. Review the current listing and in-app explanation on the device you use.
- Selected professional PDF report exports.
- Eligible CSV coordinate or data exports.
- Eligible DXF geometry exports for compatible downstream work.
- Advanced workflows and expanded history, project, and preset capacity.
- An ad-free experience while Pro access remains active.
How to choose without upgrade pressure
Start with the smallest version that completes today’s task. If you need one circumference, a sector check, a chord result, or a bolt-circle table in the browser, use the free page and verify the input. If you want the same kind of work on a phone with live diagrams and local continuity, try the free app core before evaluating a plan.
Consider Pro only after naming the constraint. “I need a DXF for this compatible workflow,” “my repeat projects exceed the free capacity,” or “I want to remove Android ads” are testable reasons. “Pro must be better for every calculation” is not a reason, because the mathematics of a named free core calculation does not become more correct merely because a subscription is active.
There is no need to decide during the first session. Compare the displayed result with a second method, inspect the free workflow over ordinary use, and open the purchase sheet later if a real limitation appears. This avoids urgency and lets the optional subscription earn its place through a feature you will actually use.
- Write down the result or file you need before choosing a tier.
- Try the matching free browser tool or named free app calculation.
- Verify units, inputs, rounding, and the geometric convention independently.
- Identify one missing Pro capability, such as an eligible export or more workspace capacity.
- Read the current device-store purchase sheet and subscribe only if that capability justifies its terms for you.
Offline use, local work, and the advertising boundary
Core calculations and the bundled pipe chart are designed to work without an internet connection in the mobile app. Purchases, advertising, support links, and sharing can require connectivity. Offline-ready therefore describes the calculation boundary; it should not be expanded into a claim that every screen, store action, or external destination works without a network.
Calculation values and local history are intended to stay on the device unless you choose to share an export. A PDF, CSV, DXF, or operating-system share action can move information outside that local boundary at your direction. Review the generated file and destination before sharing, particularly when a project name or job dimensions could be sensitive.
The public browser tools do not require a Circle account. That does not make a general promise about the entire internet connection, hosting logs, device software, or store services. Use the privacy policy for the current service description and avoid entering personal information where a geometry input needs only a dimension.
Advertising must be described by platform. Google Play marks the Android app as containing ads and in-app purchases; optional Pro includes an ad-free experience. Do not infer from that label that an iPhone build has an identical advertising surface, frequency, or consent flow. The listing and app on your actual device are the relevant evidence.
Check the store purchase sheet before confirming anything
This article intentionally publishes no fixed subscription price, billing period, discount, or trial promise. Those terms can vary by country, platform, eligibility, and time. The purchase sheet presented by the App Store or Google Play on your device is the source for the current local price and conditions immediately before confirmation.
Read whether the selected option renews, the length of its billing period, how cancellation works, and when access changes after cancellation. A download button is not consent to a subscription, and viewing a paywall is not a purchase. Confirmation happens through the store-controlled flow, where the final local terms should be visible.
If you do not want Pro, close the offer and continue with the free browser tools or the free app core. Do not enter a purchase merely to discover whether a basic result exists. The transparent order is calculation first, identified limitation second, optional plan review third.
The store buttons at the end of this guide use first-party measured redirect routes. They record only that an outbound store visit occurred with this article’s source label. A visit is not evidence of an installation, subscription, purchase, renewal, or successful use of an exported file.
You can begin now with the free Circle Calculator, compare a workshop layout in the free Bolt Circle & PCD calculator, or follow the worked one-value circle guide. Each path lets you inspect a real calculation before deciding whether the mobile free core or an optional Pro workflow is relevant.
Start with the free core
Check Circle Calculator in your device’s store.
The mobile app is free to download and its core calculations do not require a subscription. Review the current local purchase sheet only if an optional Pro workflow solves a need you can name. The buttons record an outbound visit, not an installation, subscription, or purchase.