Built by a licensed pilot. Every formula sourced.
Weight & balance, E6B and METAR. Free, on your phone.
Every formula carries a cited source and 1,239 unit tests check the answers. Each tool opens on a real worked example, so there is nothing to fill in first.
Open a tool
- Weight & BalanceCessna 172S, 172N and 152, Piper Warrior and Archer, Diamond DA 40 - watch the CG move on the envelope.
- E6BRunway crosswind, wind triangle, density altitude with a grass-strip takeoff estimate.
- METAR and TAFRaw report to plain English, with the VFR / MVFR / IFR / LIFR call and its age.
1,239
unit tests across the tools, all green
45 / 45
cells of the POH takeoff chart checked
0
accounts, logins and euros
100%
of the maths runs in your browser
Flying something else? See every aircraft profile and where its numbers come from.
Open it and it already works
No blank form, no empty chart. Each tool loads a real, computed example so you can see the shape of the answer before you type anything - then you replace the numbers with your own. These are the exact examples they open with.
Weight & balance - Cessna 172S Skyhawk SP
Two adults up front, 40 of the 53 usable gallons and a 30 lb bag, burning 18 gal on the trip.
- Takeoff weight
- 2,265 lb
- 285 lb under the 2,550 lb limit
- Takeoff CG
- 41.10 in
- limits 38.15 to 47.3 in here
- At landing
- 2,157 lb
- CG 40.75 in after the burn
- Checked at
- 3 points
- ramp, takeoff and landing, as the POH does
Inside the envelope at takeoff and still inside it at landing.
Open weight & balanceE6B
A Cessna 172 on a westerly leg, out of a warm field.
Course 270, 110 kt TAS, wind 320 at 18 kt
Heading 277, ground speed 98 kt - crab 7° right.
Field 1,200 ft, 29.92 inHg, 28 °C
Density altitude 3,048 ft - about 37% more ground roll, so a 960 ft sea-level roll becomes roughly 1,311 ft.
METAR decoder
Paste the raw report, or fetch one by ICAO code.
METAR EGLL 121750Z 21014G24KT 6000 -RA BKN012 OVC020 14/12 Q1003
MVFRmarginal VFR - ceiling 1,200 ft
- Wind 210° at 14 kt, gusting 24 kt.
- Visibility 6 km in light rain.
- Broken at 1,200 ft, overcast at 2,000 ft.
- 14 °C, dewpoint 12 °C, QNH 1003 hPa.
Why you can trust the arithmetic
This is safety-adjacent maths on a site you have never heard of. Here is what is actually behind it, all of it checkable in the source.
A pilot wrote it, not a content farm
It is built by a PPL holder out of actual general-aviation flying, and it defers to the book. The seeded loadout is worked against the POH’s own sample loading problem, and the prefilled empty weight is labelled on the page as a placeholder - because your aeroplane is not the book aeroplane.
Every constant carries its source
Each aircraft's limits and station arms are quoted from its own POH or AFM, and its type certificate data sheet where cited; the loading method from the FAA Weight & Balance Handbook (FAA-H-8083-1B) and the PHAK (FAA-H-8083-25C). Pressure altitude is the US National Weather Service formula, density altitude the 120 ft per °C rule of thumb from AOPA's density-altitude guide, and the METAR code follows FMH-1, WMO No. 306 and ICAO Annex 3. Every citation sits in the source code, next to the number it justifies.
The whole POH chart is a test
One test walks all 45 published cells of the C172S short-field takeoff chart (Fig. 5-5) and fails the build if the estimate ever comes out shorter than the printed distance. An optimistic runway number is the one error that actually hurts someone.
It stops when the rule stops
The takeoff rule of thumb is only good to 8,000 ft density altitude. Above that the tool refuses to answer and sends you to the POH chart, rather than printing a confident number that is wrong.
And it will not sign off your flight
It is a planning and training aid, not an official source, and not a certified electronic flight bag. Check every figure against the POH/AFM, your aircraft's own weight-and-balance record, current charts and an official weather briefing before you fly - you are still pilot in command. The full safety notice is at the foot of every page.
Free, offline, and out of your way
Free, with no account
No login, no email, no trial. No computed result is ever behind a payment - not the weight, not the CG, not the pass or fail against the envelope.
Works with no signal
All the arithmetic runs in your browser, so weight and balance, the E6B and paste-to-decode keep working in a hangar or a clubhouse with no bars. Looking a METAR up by ICAO code, and the runway-wind table under a decode, need a connection.
Installs to your home screen
On iPhone, in Safari tap ••• then Share, choose Add to Home Screen and leave Open as Web App on. On Android and desktop, choose Install from the browser menu. It then opens full-screen from your home screen, like an app, with no app store in the way.
No banner in your way
Cookieless, EU-hosted analytics and no advertising. Nothing here sets a tracking cookie, so there is no consent modal standing between you and the answer.
Come back to it
The fastest way to keep it is to add it to your home screen - it then opens offline, in one tap, on the walk out to the aircraft. It is also not finished: 6 airframes are modelled so far, more land as pilots ask for them, and the plan is short cockpit clips working these same calculations against real trips.