All Free Online Calculators

Firewood to buy for a camping trip by fire size and hours burned.

The last time you can start a hike and still finish before dark.

Distance walked from counted paces, calibrated to your own stride.

Real ground distance from a measurement on a paper map.

Magnification, exit pupil, and true field of view for a telescope and eyepiece.

How much more light a telescope gathers and the faintest star it can show.

Dawes and Rayleigh resolution limits and the smallest Moon feature visible.

How many times brighter one star is than another from their magnitudes.

Distance to a star from its apparent and absolute magnitude.

Distance to a nearby star from its measured parallax angle.

How large an object appears in the sky from its size and distance.

How long a planet takes to orbit a star from its orbit size.

What you would weigh on the Moon, Mars, Jupiter, and other worlds.

Moon phase, age, and illumination for any date.

Sidereal time at your longitude, the right ascension on your meridian.

Velocity change a rocket can produce from its mass and engine efficiency.

Travel time and velocity change to move between two planetary orbits.

Recession speed and distance of a galaxy from its redshift.

Event horizon size of a black hole from its mass.

Typical daily and per-feed formula amount from baby weight.

Diapers needed and total cost over a number of months.

Adjusted age of a baby born early, for milestone tracking.

Expected adult height from the parents heights (mid-parental method).

How long a frozen milk stash lasts from pumping and baby intake.

Check whether contractions match the 5-1-1 guideline for calling your provider.

Compare monthly cost of a nanny with a daycare center.

How many weeks a child needs to save allowance for a goal.

Recommended sleep for a child by age and how yours compares.

Recommended total weight gain in pregnancy from pre-pregnancy BMI.

Total and per-guest cost of a children birthday party.