Big questions.
Questionable calculations.
Useful calculators. Useless calculators.
And a few nobody should have built.
How many ducks
would fill your bath?
The ducks have not consented to this experiment.
Explore the duck maths ↗Follow your curiosity.
UK mortgage & overpayment
See your repayments, full schedule and the difference an overpayment makes.
Car finance: PCP vs HP vs loan
Compare monthly payments and the total cost to own the same car.
UK salary take-home pay
Income Tax, NI, pension and student loans for the 2026/27 tax year.
UK VAT: add or remove
Split a price into net, VAT and gross in one step.
UK property purchase tax: SDLT, LBTT & LTT
Main homes, first-time buyers and additional properties, by UK region.
Compound interest & investment growth
Separate your contributions from projected investment growth.
Credit card payoff & debt snowball
Compare minimum payments, a fixed payment and multiple-debt strategies.
BMI body mass index
Metric or imperial measurements, with WHO adult screening categories.
Calorie & TDEE
Estimate BMR, maintenance calories and a modest goal adjustment.
Macro calculator: protein, carbs & fats
Turn your calorie budget into grams with editable diet-style presets.
Daily water intake estimate
Explore a fluid-planning estimate for your size, weather and activity.
Target heart rate & training zones
Compare estimated training zones using maximum heart rate or heart-rate reserve.
Percentage calculator: 3-in-1
Percent of a number, one number as a percent, and percentage change.
Age & exact date difference
Calendar years and months, plus exact elapsed weeks and days.
Hours worked & overtime pay
A seven-day timesheet with breaks, overnight shifts and overtime.
Gravel, turf & concrete estimator
Area, volume, tonnes and whole bags or rolls for your project.
Aspect ratio & screen resolution
Scale one dimension while preserving a standard or custom aspect ratio.
Freelance day & hourly rate
Build a rate around take-home goals, overheads and realistic billable days.
Business break-even point
The sales volume needed to cover your fixed and variable costs.
Profit margin vs markup
Two percentages with two different denominators.
Stripe & PayPal merchant fees
Work backwards from the payout you want, with provider presets or your own fees.
HRT prescription cost & PPC savings
Compare annual NHS prescription costs in England, including HRT prepayment certificates.
Menopause symptom impact summary
Turn the last 14 days into a clear appointment summary, without a diagnostic score.
Menopause sleep disruption calculator
Estimate time asleep from time in bed, falling asleep and night-time awakenings.
Hot-flush pattern comparison
Compare daily episode averages across two observation periods of any length.
Night-time fan running cost
Estimate the electricity cost of running a bedroom fan overnight.
Menopause care budget planner
Plan monthly and annual out-of-pocket care costs using your own prices.
Menopause workday comfort-break planner
See how planned comfort breaks fit around a shift and lunch.
Menopause weekly movement planner
Add moderate and vigorous activity and plan strength sessions across your week.
Ducks in a bath
Your bathroom. An unreasonable number of ducks.
Coffee habit cost
Small cup. Surprisingly large number.
Your life on your phone
Just five more minutes. For thirty years.
Pizza value showdown
The bigger pizza has a point. Several, actually.
Appliance electricity
Find out what leaving it on really costs.
The snail journey
No traffic. Absolutely no urgency.
Fuel cost
Know the damage before you turn the key.
Meeting cost
There are twelve people on this call. Oh dear.
Chickens in your house
The least practical floor plan.
Hamsters to lift you
A very small, very hypothetical workforce.
Bread slices tall
A fresh perspective on your height.
Bananas long is your car
Finally, a useful unit of measurement.
Cats on your bed
You will be sleeping on the floor.
Pigeon airlift squadron
Your commute, theoretically reimagined.
Your weight in gold
You are worth your weight in something.
Lego house
The building project your feet will regret.
Can I afford this
Translate the price tag into your time.
Subscription leak
All those small monthly payments, together.
Takeaway vs cooking
Same dinner plans. Different bank balance.
Millionaire countdown
A goal, a habit and a little maths.
Pay rise estimate
What the headline rise means each month.
Inflation reality
What a steady price rise does over time.
Impulse purchase cost per use
How often will you actually use it?
Rent vs buy scenario
Compare unrecoverable costs over your chosen period.
Where did my salary go
The bit left after the necessities.
Weekends left
A reason to make next Saturday a good one.
Life spent sleeping
You have been very busy doing nothing.
Summers left
How many more ice-cream seasons?
Your life in weeks
A little perspective, one week at a time.
Lifetime commute
The journey before the actual work.
How long have you known someone
An approximate anniversary in hours.
Parent time
Make room for another cup of tea together.
Lifetime heartbeats
Your heart has been putting in the hours.
Your share of recorded history
A tiny slice of a very long story.
Bath cost
The price of a good long soak.
Shower cost
Those extra five minutes add up.
Room heating estimate
An approximate starting point for a room.
Paint required
Enough paint. Ideally just enough paint.
Moving house boxes
An educated guess for the cardboard mountain.
Fridge beer capacity
A very important logistical exercise.
Toilet roll survival
Know when to make an emergency shop.
Solar payback
When the installation could pay for itself.
Lifetime housework
Somehow the dust still comes back.
Road trip true cost
Beyond the price at the pump.
EV vs petrol
Compare annual energy spending.
Speed vs time saved
Is the faster journey really much faster?
Motorcycle tank range
How far until the next fuel stop?
Are we there yet
An answer for the back seat.
Drive for a tenner
How far does your fuel budget go?
Walking vs driving
The extra time when you leave the car.
Your car around Earth
That odometer has seen some things.
Lifetime miles to the Moon
One small drive for mankind.
Squirrels equal your weight
Your mass, in a less conventional unit.
Potatoes equal your weight
Your mass, in a less conventional unit.
Pints weigh as much as you
Your mass, in a less conventional unit.
Sausages tall
Because metres were getting a little boring.
Paperclips along your street
Because metres were getting a little boring.
Fish fingers along a blue whale
Because metres were getting a little boring.
Sausage rolls to the Moon
Because metres were getting a little boring.
Nicolas Cages tall is Big Ben
Because metres were getting a little boring.
Danny DeVitos along a jumbo jet
Because metres were getting a little boring.
Ducks in your car
An entirely theoretical capacity problem.
Grapes in your bedroom
An entirely theoretical capacity problem.
Jelly beans in your car
An entirely theoretical capacity problem.
Tennis balls in your bathroom
An entirely theoretical capacity problem.
Cups of tea in your bath
An entirely theoretical capacity problem.
Bathtubs in a swimming pool
An entirely theoretical capacity problem.
Beer to fill your house
An entirely theoretical capacity problem.
Ants carrying your shopping
Your smallest hypothetical delivery team.
Balloons to lift you
A flight of fancy, strictly on paper.
Pizzas covering a football pitch
The groundskeeper has several questions.
Salary earned on the toilet
A surprisingly productive bathroom break.
Lifetime toilet time
Everyone needs somewhere to think.
Lifetime toilet paper
Your personal paper trail.
Hangover price tag
Yesterday called. It has an invoice.
Dog cost per cuddle
Unconditional love, itemised.
Cat cost per meow
Your cat is billing by the syllable.
Child costs per day
Put your own family budget in perspective.
Takeaway lifetime cost
A regular habit, added up over the years.
Smoking habit cost
A regular habit, added up over the years.
Vaping habit cost
A regular habit, added up over the years.
Drinking habit cost
A regular habit, added up over the years.
Tea lifetime cost
A regular habit, added up over the years.
Lifetime bacon
A lifetime of little helpings.
Lifetime coffee cups
A lifetime of little helpings.
Lifetime tea cups
A lifetime of little helpings.
Lifetime potatoes
A lifetime of little helpings.
Cheapest calories
Compare food energy against the price.
Homemade pizza saving
Dough in the kitchen. Dough in your pocket.
Meal deal value
Does the deal actually deal?
One minute of work
Your working time, down to the minute.
Earnings before retirement
The remaining years, at today’s pay.
Car cost per day
Even when it sits on the driveway.
Mortgage interest total
The cost beyond the amount borrowed.
Debt cost per day
What the balance costs while it stays put.
Save £1 a day
Small daily amounts. A bigger future pot.
Save £5 a day
Small daily amounts. A bigger future pot.
Save £10 a day
Small daily amounts. A bigger future pot.
Subscriptions saved instead
What your monthly subscriptions could become.
Days alive
You have been here longer than you think.
Hours alive
You have been here longer than you think.
Minutes alive
You have been here longer than you think.
Full moons during your life
A whole lot of lunar drama.
Instagram scrolling distance
Your thumb has been on quite a journey.
Gaming PC electricity
The power behind the high score.
Phone charging cost
One battery, many tiny charges.
Unpaid overtime
The hours that never reach your payslip.
Wedding cost per guest
A celebration, divided by your favourite people.
Wedding cost per minute
Make every minute count. Literally.
Relationship miles
Going the distance, quite literally.
Missing something? Request a calculator ↗