Kraken Sails · Rating Tools
Sail Area Calculator
Enter your sail measurements to see the area under ORC, IRC, PHRF and AMS, test whether a code sail measures as a headsail or a spinnaker, and see which dimensions each rule charges for.
Limits: this tool calculates rated sail area and rule classification, not your rating (TCC, GPH or PHRF number). ORC and IRC formulas are the published ones; the IRC mainsail and all AMS figures are indicative because those formulas are not published, and PHRF varies by region. It is not a measurement certificate. Read all limits
Mainsail
How the sail is set
Rig dimensions (optional)
Used for ORC rated minimums, PHRF standard dimensions and LP%.
Area by rating rule
Rated area for the sail entered.
Enter the required (*) measurements to calculate.
Shape check
Schematic from your measurements. The dashed outline is your saved baseline.
Headsail or spinnaker?
How this sail classifies under each rule, based on half width ÷ foot (both measured as a spinnaker), battens, how it is set and where it is tacked.
Rule efficiency
How much rated area each rule adds when you lengthen one dimension, compared with the actual sail area gained.
Free: rule ignores itCheap: actual gain exceeds rated gain by more than 10%Costly: rated gain exceeds actual gain by more than 10%Cheap/costly shading is shown for published formulas only
Baseline vs. what-if
Save the current design as a baseline, change the dimensions (shorter luff, wider head, more roach), and compare rated area under each rule.
No baseline saved for this sail type.
Email this summary
We’ll email you the measurements, areas, classification and any baseline comparison for the sail on screen. A copy goes to Kraken Sails.
Limits of this tool
Read these before you rely on any figure here.
- Area, not rating. The tool shows rated sail area and classification. It does not predict a TCC, GPH, AMS rating or PHRF number. ORC ratings come from a VPP, IRC’s TCC formula is unpublished, and the effect of the same area change differs from boat to boat.
- ORC. Uses the published measured-area formulas (rules 109, 111, 113, 114) and applies the rated minimums only when you enter rig dimensions. It leaves out the boom, mast-section and rotating-mast additions to mainsail rated area, and rates one sail at a time, while ORC rates the largest sail of each type in your inventory.
- IRC. Headsail (HSA), flying headsail (FSA) and spinnaker (SPA) areas use the published formulas. IRC publishes no mainsail area formula, so the mainsail figure is an indicative trapezoid built from the dimensions IRC declares (P, E, MHW, MTW, MUW).
- AMS. AMS publishes measurement definitions but no area or rating formulas. Every AMS figure here is indicative: an ERS-style area built only from the dimensions AMS measures.
- PHRF. PHRF is administered regionally and rules differ. Spinnaker area uses the PHRF-LO method; the mainsail (P × E / 2) and headsail (LL × LP / 2) figures are proxies, because most regions rate those sails on P, E and LP% rather than area.
- Estimated actual area. For mains and headsails this is a smooth curve fitted through your measured widths. It is a model of the sail, not a measurement, and a different curve would give a slightly different answer. Spinnakers use the ERS three-station area.
- Efficiency figures. “Free”, “cheap” and “costly” describe rated area only. A dimension a formula ignores can still affect rating through the VPP, sail coefficients, girth limits or certificate maximums.
- Headsail or spinnaker test. Checks half width ÷ foot, battens, how the sail is set and where it is tacked. It does not check every condition: for example IRC’s STLFHmax tack limit and centreline requirement, ORC’s HLP ≤ 1.1·J limit for inner flying sails, luff and pole limits, measurement tolerances or class rules.
- Defaults. Blank widths use ORC no-roach defaults and are flagged. Real measurements give a real answer.
- Rule versions. Based on ORC Rating Systems 2026 and the IRC Rule as amended for 2026. Rules change every year.
- Not a certificate. Figures depend on correct measurement to ERS. Confirm anything that matters with an accredited measurer or your rating authority.
Glossary
Measurement names and rating terms used in this calculator. Tap the ? next to any input to jump here.
Sources: ORC Rating Systems 2026 · IRC Rule (21.6.2, 21.7.2, Appendix A; 2026 changes) · PHRF-LO spinnaker area · AMS/SMS Rules Book (measurement definitions) · World Sailing Equipment Rules of Sailing (ERS).