Calculators
Free, no sign-up, and they show their working. Every default is visible and editable, and every one says what it assumes.
If you're thinking about starting
If you fly
What is a hot day doing to my launch?
Density altitude
Takes: field elevation, temperature and altimeter setting
Is buying a glider actually cheaper than renting one?
Own, share, or club glider?
Takes: a purchase price, your hours and the club rate
Which weather product should I actually pay for?
Which soaring forecast covers your region
Takes: nothing — it is a comparison, not a calculator
How fast should I be flying, and why is the tangent there?
Polar and speed to fly
Takes: three numbers off your flight manual's polar page
How do these two gliders actually compare?
Glider polar comparison
Takes: nothing — it is a sourced library, not a calculator
Why did I score that, and would another rulebook agree?
Contest scoring
Takes: a day's distances, times and handicaps
What is my competition handicap, and which way does it work?
Glider handicaps
Takes: your glider and its takeoff mass
How much height do I need, and how wrong could it be?
Final glide sensitivity
Takes: your polar, a distance, and what the air is doing
Should I be carrying water today?
Ballast and the thermal
Takes: your polar, your stall speed, and how wide the thermals are
How much of that wind is across the runway?
Crosswind component
Takes: a runway, a wind direction and a wind speed
How high will the thermals actually go?
Thermal index
Takes: a sounding and a forecast maximum temperature
What heading, and what does the wind cost me?
Wind triangle
Takes: a course, a true airspeed and a wind
How far does the centre of gravity move?
Weight shift
Takes: a weight, where it moves from and to, and your all-up weight
How high will the cumulus be today?
Cloud base
Takes: a surface temperature and either a dew point or a humidity
How close to the stall am I actually working?
The lift equation
Takes: your mass, wing area and the air you are flying in
What is a steep turn doing to my wings and my stall speed?
Load factor and bank angle
Takes: a bank angle, and your wings-level stall speed
How tight a circle can I actually fly?
Turn radius and rate
Takes: a speed, a bank angle and the altitude you are at
How much faster am I really going than the ASI says?
True airspeed
Takes: your indicated airspeed, altitude and outside air temperature
What altitude am I actually at?
Altimeter settings and altitude
Takes: what your altimeter reads and what it is set to
Is this glider in balance with me in it?
Weight and balance
Takes: the weighing report and placard for the glider you are flying
If you help run a club
What does a launch actually cost our club to provide?
Launch cost: aerotow vs winch
Takes: your fleet, your fuel price and your launches per year
How many more intro flights can we sell?
Nonmember income headroom
Takes: your gross receipts split into member and nonmember income
What should we be putting aside to replace the trainer?
Fleet reserve
Takes: a replacement price, a trade-in, and how long you have
The reasoning behind them
8 of these 24 have a written guide behind them, explaining where the numbers come from and what they assume — part of a set on the practical side of flying and running a gliding club. The rest state their assumptions on the calculator itself, which is the minimum either way.
Read the guides →More coming, slowly and on purpose
Every one of these had to earn its place by answering a question somebody actually works out by hand, and each shows its assumptions rather than just its answer. If there's a number you calculate every season and wish you didn't have to, tell us what it is.