Gradient Unit Converter (ft/nm · % · degrees · m/km)
All four gradient dialects interconverted from any one — aviation's ft/nm, engineering's percent, trigonometry's degrees and the metric world's m/km.
Handy anchors: the 200 ft/nm IFR standard is 3.3%; a 3° glideslope is 5.2% or 318 ft/nm; runways top out near 2%; and percent ≈ degrees × 1.75 for small angles.
Formula
⚠️ For planning and education only. Weight & balance must be computed from YOUR aircraft's actual empty weight, arm and current equipment list, and verified against the POH/AFM envelope before flight.
All four gradient dialects interconverted from any one — aviation's ft/nm, engineering's percent, trigonometry's degrees and the metric world's m/km.
About Gradient Unit Converter (ft/nm · % · degrees · m/km)
Aviation alone speaks gradient four ways: departure charts in ft/nm, approach plates and runway slopes in percent, glide and descent geometry in degrees, and metric AIPs in metres per kilometre. This converter accepts any one and returns all four, locked consistent — plus the anchor equivalences (200 ft/nm = 3.3%; a 3° ILS = 318 ft/nm) that make chart numbers intuitive rather than memorized.
How to use Gradient Unit Converter (ft/nm · % · degrees · m/km)
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula % = rise/run × 100; ft/nm = % × 60.76; m/km = % × 10; ° = atan(%/100) substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Gradient Unit Converter (ft/nm · % · degrees · m/km)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula % = rise/run × 100; ft/nm = % × 60.76; m/km = % × 10; ° = atan(%/100) with sources cited on the page
- ✓Handy anchors: the 200 ft/nm IFR standard is 3.3%; a 3° glideslope is 5.2% or 318 ft/nm; runways top out near 2%; and percent ≈ degrees × 1.75 for small angles.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Is a 3° glideslope the same as 3%?+
No — small-angle near-miss territory: 3° is tan(3°) = 5.24%, or 318 ft/nm, or the familiar ~300 ft per mile rule. The 'percent ≈ degrees' confusion understates slopes by 75%. For quick mental conversion, percent ≈ degrees × 1.75 below about 15°.
Why does aviation use nautical-mile gradients but metric elsewhere?+
History plus the knot: distances and speeds in nm/kt make ft/nm multiply cleanly into ft/min via GS/60 (our required-rate tool). ICAO's metric states publish m/km in AIPs — numerically just percent × 10 — and Annex 14 runway slopes are percent worldwide. Four dialects, one geometry; this page is the phrasebook.
What are the gradient numbers worth memorizing?+
Five anchors cover most flying: 200 ft/nm (3.3%) — IFR departure default; 318 ft/nm (5.2%, 3°) — standard glidepath; 152 ft/nm (2.5%) — the TERPS 40:1 surface itself; 1,000 ft/nm ≈ 16.5% — strong light-single Vx territory; and 6,076 ft/nm = 100% = 45° as the scale's sanity check.
How do I use this for descent planning?+
The same geometry runs downhill: a 3° descent needs ~300 ft per nm, so losing 9,000 ft takes 30 nm — the '3-to-1' rule. Convert any desired angle to ft/nm here, multiply your GS by it over 60 for the VSI target (e.g. 3° at 150 kt GS ≈ 795 fpm). Gradient literacy is bidirectional.
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