About

Rubber stamps follow strict geometric rules. Circular text must be kerned along an arc of radius r, with each character offset by θ = wr, where w is the character width in pixels. Poor spacing produces illegible impressions that fail official document requirements in many jurisdictions. This tool calculates arc distribution, handles multi-line center text, and renders at 4× resolution for print-quality output. It approximates real engraving by inverting colors and applying border patterns consistent with ISO 16684 graphic standards. Limitation: font rendering depends on system-installed typefaces and may vary between operating systems.

Upload a vector-style logo (PNG with transparency recommended), select from circle, rectangle, ellipse, or diamond shapes, and configure border width, inner rings, and star decorations. The output is a transparent-background PNG suitable for digital watermarking or physical stamp ordering. Pro tip: commercial stamp manufacturers typically require 300 DPI minimum - set canvas size to at least 600px for a 2in stamp.

Formulas

Circular text rendering distributes characters along an arc. For a string of n characters, each character i is placed at angular position θ_i computed from cumulative character widths:

θ_i = θ_start + i∑k=0 w_kr

Where w_k is the measured pixel width of character k (via measureText), and r is the arc radius in pixels. The starting angle θ_start is offset so the text is centered:

θ_start = −12 ⋅ W_totalr

Where W_total = n∑k=0 w_k is the total arc length of all characters. For bottom-arc text, characters are rendered upside-down with θ progressing clockwise. The export resolution multiplier s = 4 ensures output at effectively 300+ DPI for a standard stamp diameter.

Reference Data

Stamp Type	Typical Shape	Diameter / Size	Common Use	Text Lines	Logo
Corporate Seal	Circle	40mm	Legal documents, contracts	2 arced + center	Yes
Notary Stamp	Circle	38 - 42mm	Notarization, affidavits	2 arced + center	State emblem
Address Stamp	Rectangle	60×25mm	Return address, envelopes	3 - 4 lines	Optional
Date Stamp	Rectangle	47×18mm	Received/approved marking	1 - 2 lines	No
Inspection Stamp	Circle	12 - 20mm	QC pass/fail marking	1 arced	Number
Teacher Stamp	Circle / Star	25mm	Grading, motivation	1 arced	Emoji/Star
Library Stamp	Rectangle	50×30mm	Book ownership marking	2 - 3 lines	Optional
Medical Stamp	Rectangle	58×22mm	Prescriptions, doctor ID	3 - 5 lines	Caduceus
Customs Stamp	Circle / Oval	35mm	Border control, passports	2 arced + date	National emblem
Wax Seal Style	Circle	30 - 35mm	Invitations, branding	1 arced	Monogram
Self-Inking Round	Circle	20 - 50mm	General office use	1 - 3 arced	Optional
Pocket Stamp	Rectangle	38×14mm	Signature, name stamp	1 - 2 lines	No
Monogram Stamp	Circle	30mm	Personal branding, stationery	1 arced	Initials
Confidential Stamp	Rectangle	55×15mm	Document classification	1 bold line	No
Event / Wedding Stamp	Circle / Oval	45mm	Invitations, favors	2 arced + date	Heart/Rings

Frequently Asked Questions

Most stamp manufacturers require at least 300 DPI. For a 40 mm diameter stamp, that translates to approximately 472 pixels. This tool renders at 4× internal resolution (default canvas 600 px produces 2400 px output), which exceeds 300 DPI for stamps up to 5 inches in diameter.

Canvas text rendering uses system fonts. The same font name may have different metrics (character width, baseline offset) across operating systems. Sans-serif fonts like Arial have the most consistent cross-platform rendering. For critical applications, test the exported PNG on the target platform before ordering.

Yes. PNG files with alpha transparency are fully supported. The tool composites the logo onto the stamp canvas preserving transparency. JPEG files have no alpha channel and will render with a white background. For best results, use a monochrome PNG logo with transparent background.

Traditional rubber stamps are single-color (the ink pad color). This tool generates monochrome output by design. To simulate a two-color effect, generate two separate stamps with different color settings and layer them in an image editor. Some modern self-inking stamps do support dual-color pads with a physical divider.

Characters will overlap when the total arc length exceeds the available circumference. The tool calculates W_total / r and if the resulting angle exceeds approximately 300°, text becomes illegible. Reduce font size, abbreviate text, or increase the stamp diameter. The preview updates in real time so you can see the effect immediately.

Yes, the PNG export uses a transparent background by default. The stamp graphic (borders, text, logo) is rendered on a clear canvas. This allows you to overlay the stamp on documents, photos, or colored backgrounds without a white box.