MAINSPRING CALCULATOR
Professional Watch Repair Software
by RedRoosterUK.co.uk
TIRED OF ORDERING THE WRONG MAINSPRING?
If you've ever measured a barrel, guessed at the spring size, ordered from a supplier, and then found it doesn't fit — you know how frustrating (and expensive) that is.
This calculator takes your barrel measurements and tells you exactly what mainspring you need: the height, thickness, length, and material. No more guesswork. No more wasted orders.
Works for watches AND clocks — manual wind, automatic, pocket watches, and clock movements.
WHAT YOU GET
✓ Mainspring Calculator — HTML software, runs in any web browser
✓ User Guide PDF — full instructions with measurement reference tables
✓ Single-user commercial license — use it in your workshop or business
✓ All files on a USB stick — plug in and go, nothing to install
HOW IT WORKS
1. Measure your barrel (internal diameter, depth, and arbor diameter)
2. Select your watch type and desired power reserve
3. Click Calculate — get your recommended mainspring specs instantly
That's it. Three measurements in, full spring specification out.
FEATURES
● Calculates spring height, thickness (with range), and length from barrel dimensions
● Verify mode — check whether a spring you already have will fit your barrel
● Interactive diagram — see the spring inside the barrel in real time as you type
● Top-down view with Archimedean spiral + cross-section showing height clearance
● Drag handles to resize barrel/arbor visually
● Animated winding demonstration
● 6 built-in presets: ETA 2824-2, ETA 2892-A2, Miyota 9015, Unitas 6497, Sellita SW200, Seiko NH35
● Colour-coded fill ratio indicator (green = ideal, amber = tight, red = overfilled)
● Copy results to clipboard — paste straight into a supplier order
● Print-friendly output with your caliber reference
● Dark and light themes (great for bench use under bright lighting)
● Thickness reference chart for all watch and clock types
NO INSTALLATION NEEDED
This is a single HTML file. Double-click it and it opens in your browser. Works on:
✓ Windows (Chrome, Firefox, Edge) ✓ Mac (Safari, Chrome, Firefox)
✓ iPad / Android tablet ✓ Phone (responsive design)
✓ No internet required after first open ✓ No subscription — you own it forever
WHO IS THIS FOR?
● Watch repairers who order mainsprings regularly
● Hobbyist watchmakers working on different calibers
● Clock repairers (covers clock and mantle clock springs too)
● Horological students learning about barrel mechanics
● Anyone who's tired of cross-referencing catalogues and guessing
SHIPS ON USB STICK
Ships on a branded USB stick via Royal Mail. Includes the calculator software, full user guide PDF, and your license. Plug in and open — works immediately in any web browser, no installation needed.
Important: All calculations are estimates based on standard horological formulas. Always verify results against supplier specifications before ordering. This tool works alongside supplier catalogues, not instead of them.
