Solutions Atlas
Calculators and conversions. More tools will be added here — they'll run fully in the browser.
True wind from apparent
Inputs: apparent wind speed (AWS), apparent wind angle (AWA, off the bow), boat speed (BS).
TWS = √(AWS² + BS² − 2·AWS·BS·cos(AWA))
TWA = atan2(AWS·sin(AWA), AWS·cos(AWA) − BS)
Apparent wind from true
The inverse — useful before trimming for a known true-wind condition, or when you're given a forecast TWS/TWA (e.g. from a GRIB) and want to know what the instruments should read.
Inputs: true wind speed (TWS), true wind angle (TWA, off the bow), boat speed (BS).
AWS = √((TWS·sin(TWA))² + (TWS·cos(TWA) + BS)²)
AWA = atan2(TWS·sin(TWA), TWS·cos(TWA) + BS)
Sanity check: with TWS = 12 kt at TWA = 60°, BS = 6 kt, expect AWS ≈ 15.9 kt, AWA ≈ 41° (wind shifts forward as you bear through it).
Pressure unit conversions
- 1 inHg = 33.8639 mb (hPa)
- 1 mb = 1 hPa = 0.02953 inHg
- Standard atmosphere = 1013.25 mb = 29.92 inHg
Temperature / dewpoint / humidity
- Dewpoint depression (T − Td): < 2°C with light wind over water ≈ fog risk.
- Approx dewpoint from RH: Td ≈ T − (100 − RH) / 5 (°C, good for RH > 50%).
Distance / speed
- 1 nm = 1.852 km = 1.1508 statute mi
- 1 kt = 1 nm/h = 0.5144 m/s
- Wind speed ft/s = kt × 1.688