Home life, family and pets

Ages and birthdays, saving up for the thing that has been asked for every day this month, where the week actually goes, what the dog eats in a year and what the heating costs. Small sums, the kind you do on the back of an envelope and then lose. Keep them in a note instead and they answer themselves next time.

Ages, birthdays and sleeps

Give a birth date a name and the note will tell you where everyone is without you counting on your fingers.

calcAnswers depend on today’s date or live dataCopy

ada = 14 March 2016 gives March 14, 2016

whole years since ada gives 10 years

# The next big one

ada + 18 years gives March 14, 2034

days until 14 March 2027 gives 177 days

weekday on 14 March 2027 gives Sunday

# The bit that matters to a six-year-old

sleeps until 25 December 2026 gives 98 days

sleeps until 31 October 2026 gives 43 days

whole years since a birth date is somebody’s age, and weekday on tells you whether the birthday lands on a Saturday before you promise a party. sleeps until is the same count as days until, said the way it gets said at bedtime. These all count from today, so the note is right every morning without being edited. See Counting down.

Pocket money and saving up

The bike costs £180 and pocket money is £3.50 a week. That sum has an answer, and it’s much more convincing written down.

calcCopy

pocket money = £3.50/week gives £3.50/week

bike = £180 gives £180.00

Weeks of saving: bike / pocket money gives 51.4285714286 weeks

# With half of the birthday money on top

birthday = £40 gives £40.00

(bike - birthday) / pocket money gives 40 weeks

# Jobs around the house, £2 a time, twice a week

extra = £2 * 2 gives £4.00

bike / (pocket money + £4/week) gives 24 weeks

pocket money in £/year gives £182.62/year

# What a fiver a week comes to by eighteen

£5/week * 10 years gives £2,608.88

A price divided by an amount per week comes out in weeks, and adding the jobs money cuts the wait to less than half, which is a better argument than any amount of explaining. See Prices per unit.

The shape of the week

Written down, the week stops being a blur.

calcCopy

# Weeknights, from tea to lights out

tea = 5:30pm gives 5:30 PM

bedtime = 7:30pm gives 7:30 PM

tea to bedtime gives 2 hours

# Reading, twenty minutes a night

20 min * 7 in hours gives 2.3333333333 hours

20 min * 365 in hours gives 121.6666666667 hours

# Screen time, an hour on weekdays and two at the weekend

1 hour * 5 + 2 hours * 2 gives 9 hours

9 hours is what % of (7 * 14 hours) gives 9.1836734694%

# Three of us sharing the washing up

21 meals / 3 gives 7

tea to bedtime between two clock times gives what’s in between, and multiplying a nightly habit by 365 shows what it adds up to over a year: twenty minutes of reading a night is more than five whole days. See Adding time to a clock time.

The pets

A sack of food, a monthly bill and a dose that depends on how heavy the animal is.

calcCopy

# A 22 kg dog

dog = 22 kg gives 22 kg

food = 320 g/day gives 320 g/day

sack = 12 kg gives 12 kg

Sack lasts: sack / food gives 37.5 days

sack / food in weeks gives 5.3571428571 weeks

feeding = £38 / (sack / food) gives £1.01/day

feeding in £/year gives £370.11/year

# The worming tablet says 2 mg per kilo

dog * 2 mg/kg gives 44 mg

# What the dog costs a year, all in

insurance = £18/month gives £18.00/month

vet = £240/year gives £240.00/year

dog costs = insurance + vet + feeding gives £2.26/day

dog costs in £/year gives £826.11/year

dog costs in £/month gives £68.84/month

A weight over an amount per day gives the days it lasts, and the price over those days gives what the animal costs to feed each day. A dose written per kilo times the animal’s weight gives the amount on the packet, which is worth checking twice rather than once. See Rates with per and /.

Doses, packets and refills

Counting tablets out of a packet, so you know whether you need another before the weekend.

calcCopy

# Two tablets, three times a day, for a week

2 tablets 3 times a day * 7 days gives 42

# The packet holds 32

ceil(42 / 32) gives 2

# A 200 mL bottle, 5 mL twice a day

200 mL / (5 mL * 2) gives 20

# Enough for a fortnight away

2 * 3 * 14 gives 84

# A repeat prescription of 90 days, ordered a week early

90 days - 1 week gives 11 weeks 6 days

The first line reads like the label on the box. Rounding up says how many packets to pick up, and the bottle line says how many days it lasts. See Rates with per and /.

Keeping the house warm

Your bill prints kilowatt-hours and a rate in pence. Put both in a note and it will tell you what anything costs to run.

calcCopy

# Last year's bill

gas used = 8,400 kWh/year gives 8,400 kWh/year

gas rate = 6.4p/kWh gives £0.064/kWh

power used = 2,900 kWh/year gives 2,900 kWh/year

power rate = 24.5p/kWh gives £0.245/kWh

standing = 62p/day gives £0.62/day

energy = gas used * gas rate + power used * power rate gives £1,248.10/year

bill = energy + standing gives £4.04/day

bill in £/year gives £1,474.55/year

bill in £/month gives £122.88/month

# One load of washing, and drying it the easy way

0.9 kWh * power rate gives £0.22

2.5 kWh * power rate gives £0.61

# Turning the thermostat down one degree saves about 8%

energy * 8% gives £99.85/year

Every line is an amount per period, so the yearly usage and the daily standing charge add together without you converting either one first, and in £/year or in £/month reads the total however you want it. The monthly figure is what the direct debit will be. The last two pairs are the ones worth pinning up: the dryer costs about three times what the washing machine does, and a degree off the thermostat is a hundred pounds. See Cents and pence.

Make it your own

• Work out when a baby is due, or when someone is back: today + 40 weeks and 18 August 2026 + 12 weeks.
• Check a school holiday: workdays between 20 July 2026 and 2 September 2026 gives 32 workdays to cover.
• Share the driving, the cooking or the bins fairly: 21 meals / 3 gives seven each, and 52 weeks / 4 gives thirteen turns a year.
• Price a takeaway against cooking: £46 - £10.80 shows the difference on a Friday night, and * 52 shows the year.
• Split a family holiday by who sleeps where: £1,800 / 5 nights gives £360.00 a night.
• Convert a child’s height for the grandparents: 128 cm in feet and inches gives 4 feet 2.39 inches.
• Keep a meter reading note: two readings and 4,921 - 4,608 gives 313 kWh used, then * 24.5p/kWh gives £76.69.
• Work out a fair rate for the babysitter: 7:30pm to 11:45pm at £12/hour gives £51.00.
• See what a daily coffee habit costs: £3.20/workday * 46 weeks gives £736.00.
• Count what’s left of the holidays: days until 2 September 2026 and weekday on 2 September 2026.
• Tag the household spending as you go with #house or #kids, and put total of #kids at the bottom. See Tags.