🧮Calculators
Calculators cover finance, health, math, physics, engineering and everyday life: interest and loans, net salary, BMI, rule of three, conversions and more. Results are informational and educational — for important decisions, confirm with a professional and official sources.
2904 tools
Bedtime Calculator (90-Minute Cycles)
Enter the wake-up time in HH:MM and get two times to lie down, counting back 5 and 6 sleep cycles plus 14 minutes to doze off: 07:00 gives 23:16 and 21:46.
Wake-Up Time by 90-Minute Sleep Cycles
Enter the hour you go to bed and get three suggested alarms, after 4, 5 or 6 cycles of 90 minutes plus the 14 minutes it takes to fall asleep.
REM Sleep Countdown
From your bedtime and total hours asleep, estimates the clock time of the first REM phase, roughly 104 minutes in, and how many 90-minute cycles fit.
Melatonin Timing Calculator
Enter the bedtime you are aiming for and it subtracts a fixed 2 hours to show the clock time to take melatonin, the usual sleep onset window.
Sleep Debt Calculator
Calculate your weekly sleep debt by comparing the hours you actually slept with your ideal target. Find out how much rest you need to catch up on.
Sleep Efficiency Calculator (TST/TIB)
Minutes asleep divided by minutes in bed, times 100, with a rating: 90 percent or more counts as excellent, under 80 percent as poor sleep.
Ethereum Gas Fee Calculator
Gas used times the gwei price gives the cost in ETH, then the ETH/USD rate you type converts it: 21000 gas at 30 gwei comes to 0.00063 ETH.
Bitcoin Transaction Size Estimator in Bytes
Enter the number of inputs and outputs to estimate 10 + 148 per input + 34 per output bytes, plus the SegWit vByte figure at about 60%.
Crypto Mining Profitability by kWh Cost
Enter hashrate in TH/s, USD per TH per day, rig draw in kW and your kWh price to get daily revenue, power cost (kW x price x 24) and net profit.
Bitcoin Halving Countdown
Type a reference date and get the days and years left until the next Bitcoin halving, estimated for April 2028, when the block reward falls to 1.5625 BTC.
Bitcoin Block Reward by Year
Enter a year to see the block subsidy in BTC after each halving: 50 in 2009, 6.25 in 2020, 3.125 in 2024 and 1.5625 in 2028; later dates are estimates.
ERC-20 Transfer Cost Calculator
Estimate the cost of an ERC-20 token transfer (about 65k gas) on the Ethereum network. Enter the gas price and see the total in ETH and US dollars.
IPv6 Subnet Calculator
Calculate how many hosts and subnets fit in an IPv6 prefix (/n). A tool for network administrators planning IPv6 addressing.
TCP Bandwidth-Delay Product
Multiplies link bandwidth in Mbps by round-trip time in milliseconds to size the TCP window that keeps the pipe full, reported in bytes, KB and MB.
MTU Calculator by Tunnel Encapsulation
Subtracts tunnel overhead from a base MTU of 1500 bytes: PPPoE 8, GRE 24, VXLAN 50, IPsec 56. Returns the effective size to set on the link.
MSS from MTU: TCP Maximum Segment Size
Subtracts the IP and TCP headers from a link MTU, 40 bytes on IPv4 and 60 on IPv6, so 1500 leaves 1460 and 1440 bytes of payload per segment.
TCP Window Scaling Factor Calculator
Enter a target receive window in KB to get the TCP window scale shift count needed past the 64 KB limit, plus the maximum effective window in bytes.
IPv4 Subnet Host Count
Enter a CIDR prefix from 0 to 32 for total addresses and usable hosts, 2^(32−n) − 2 after network and broadcast, with /31 and /32 handled separately.
CIDR Network Calculator
Calculate the network address, broadcast, mask and host range from an IP in CIDR notation. An essential tool for network and subnet administration.
Data Retention Deadline by Purpose (Brazil)
Enter the start date and pick tax, labor, social security, consumer or medical records to get the delete-after date under Brazilian rules: 5, 10 or 20 years.
Earth to Sun Distance in AU by Date
Pick a calendar date and get the Sun distance in astronomical units and km from orbital eccentricity 0.01671: 0.9833 AU in early January, 1.0167 AU in July.
Earth Orbital Speed by Date Calculator
Enter a date to see how fast the planet is moving along its orbit, in km/s and km/h: 30.28 km/s near perihelion in January, 29.29 km/s at aphelion.
Kepler Third Law: Orbital Period
A semi-major axis in astronomical units returns the period around the Sun, T equal to the square root of a cubed. Mars at 1.524 AU orbits in 1.88 years.
Distance Modulus to Magnitude
Calculate the apparent magnitude of a star from its absolute magnitude and distance. Essential in observational astronomy and astrophysics.
Redshift z to Recession Velocity
Enter redshift z to get both the non-relativistic v = c·z and the relativistic Doppler speed in km/s, plus the fraction of c. z = 0.01 returns 2998 km/s.
Relativistic Doppler Shift Calculator for Light
Enter source frequency in Hz and radial velocity in km/s, positive when receding, for the observed f = f0 * sqrt((c-v)/(c+v)) and the shift.
Schwarzschild Radius Calculator
Calculate the Schwarzschild radius (event horizon) of a black hole from its mass, using the formula r_s = 2GM/c². Result given in meters.
Dough Hydration Calculator
Calculate dough hydration with baker percentage (water ÷ flour × 100). Essential for getting bread, pizza and sourdough just right.
Sourdough Starter Feeding Calculator
Enter the weight of your ripe culture in grams and pick a 1:1:1, 1:2:2 or 1:5:5 refresh to get the flour and water in grams plus the total after feeding.
Brine Calculator by Salt Percentage
Enter the water weight in grams, the percent of salt by weight and the meat weight to get grams of salt to dissolve and soaking time at 1 hour per kg.
Dry Pasta Portion per Person Calculator
Multiplies the number of guests by the grams of dry pasta each one eats, 100 g by default and adjustable from 80 to 120 g, for the total to cook.
Sauce Reduction Ratio Calculator
Starting and target volume in ml give the reduction factor and the share of liquid boiled off: 1000 ml down to 250 ml is 4.00x, or 75 percent.
Salt as a Percentage of Meat Weight
Enter raw meat weight in grams and a salt percentage, 1% to 2% for a dry brine, to get how much salt to weigh out: 1000 g seasoned at 1.75% needs 17.5 g.
Recipe Scaling Calculator
Multiplies one ingredient amount by target servings over original servings, so 200 g for 4 people becomes 300 g for 6; run it once per ingredient.
Caffeine by Drink Calculator
Estimate how many milligrams of caffeine you drink per day by adding up coffee, tea, energy drinks and sodas. Pick the type and the number of servings.
Oven Preheat Time Calculator
Divides the target temperature in °C by 20, with a floor of 5, to estimate how long a home oven warms up: 200 °C takes 10 minutes, 250 °C takes 13.
De Broglie Wavelength Calculator
Enter a particle momentum in kg·m/s and get its matter wavelength in meters from λ = h ÷ p, with Planck constant h = 6.62607015e-34 J·s.
Heisenberg Uncertainty Calculator
Calculate the Heisenberg uncertainty principle: from the position uncertainty, get the minimum momentum uncertainty (or vice versa). A pillar of quantum physics.
Photon Energy Calculator (E=hf)
Calculate the energy of a photon from its frequency using the Planck equation (E = h·f). Fundamental in quantum physics, optics and spectroscopy.
Photon Momentum Calculator
Calculate the momentum of a photon from its energy (p = E/c). A fundamental concept in quantum physics and radiation pressure.
Particle in a Box: Energy Level E_n
Enter quantum number n, mass in kg and well width L in meters to get the energy in joules from E_n = n^2 h^2 / (8 m L^2), with h = 6.626e-34.
Particle in a Box: First Five Energy Levels
Enter the well length in nanometers and get n = 1 to 5 for an electron, as multiples of E1 and in eV, from E_n = n^2 h^2 / (8 m L^2).
Bohr Radius Calculator
Calculate the Bohr orbit radius for the hydrogen atom with the formula r = n²·a₀, where a₀ is the Bohr radius (≈ 5.29×10⁻¹¹ m).
Rydberg Formula Wavelength Calculator
Enter the levels n1 and n2 to get the hydrogen spectral line in metres: 1/λ = R·(1/n1² − 1/n2²), R = 1.0974e7 m⁻¹. From n=3 to n=2 gives 656 nm.
Wien's Displacement Law Calculator
Calculate the peak wavelength of a black body using Wien's displacement law from temperature. Find the dominant color of stars and hot objects.
Blackbody Peak Frequency (Wien)
Calculate the peak frequency of blackbody radiation with Wien law (f_max ≈ 5.879×10¹⁰·T) from the temperature in kelvin.
UK VAT Calculator (20%)
Calculate UK VAT (the 20% standard rate) on a net or gross amount. Add the tax to a price or break out the VAT already included.
German VAT (MwSt) 19% Calculator
Adds the German 19% Mehrwertsteuer to a net amount or strips it out of a gross one, showing the tax due and the other side of the figure in euros.
France VAT (TVA) Calculator
Calculate French VAT (TVA at 20%) on any amount and see the price with and without tax. Handy for shopping, invoices and business in France.
Spain VAT (IVA) Calculator
Calculate the standard Spanish VAT (IVA at 21%) on any amount and see the total with and without tax. Great for shopping, invoices and business in Spain.
Italy VAT (IVA) Calculator
Calculate the standard Italian VAT (IVA at 22%) on any amount and see the price with and without tax. Handy for shopping, invoices and business in Italy.
Canada GST Calculator
Calculate Canadian GST (5% federal) with the option to add provincial tax (PST/QST). See the final price with taxes for purchases and invoices.
Ontario HST Calculator
Calculate Ontario HST (13% harmonized sales tax) on any amount and see the price with and without tax. Great for shopping and invoices in Canada.
California Sales Tax Calculator
Calculate California sales tax (7.25% minimum state rate, excluding local taxes) on an amount. Add the tax or break out what is already included.
New York Sales Tax Calculator
Pick New York City, Buffalo or Albany, enter a pre-tax amount in dollars and get the combined state and local sales tax, the total due and the rate applied.
Australia GST Calculator
Calculate Australian GST (10% tax) on any amount and see the total with and without tax. Great for shopping, invoices and business in Australia.
Singapore GST Calculator
Calculate Singapore GST (9%) on any amount and see the price with and without tax. Handy for shopping, invoices and business in Singapore.
India GST Calculator
Calculate Indian GST by selecting the rate slab (5, 12, 18 or 28%) and see the total with and without tax. Great for shopping, invoices and business.
NPV (Net Present Value) Calculator
Compute project Net Present Value (NPV) from a cash flow series and discount rate. Decide if a project adds value (NPV > 0).
IRR (Internal Rate of Return) Calculator
Find IRR of a cash flow via Newton/bisection. Also displays NPV at the solution point.