Tap any envelope to mark it filled, and tap it again if you got it wrong. With a keyboard, Tab to the grid, move with the arrow keys and press Enter. Your progress is saved in this browser only. Nothing gets uploaded and there's no sign up.
How the 100 envelope challenge works
Number 100 envelopes from 1 to 100. Each envelope holds its own number: envelope 1 gets 1, envelope 37 gets 37, envelope 100 gets 100. Whenever you save, pick an envelope at random, put that amount inside and set it aside. When the last one is full, you're done.
That's the whole thing. The random draw is what makes it work. Some days you pull a 4 and it's easy. Some days you pull a 96 and it hurts a bit, but you knew one of those was coming.
How much it adds up to: 5,050
Fill all 100 and you've saved 5,050. You don't need a calculator to see why. Pair the envelopes from both ends: 1 and 100 make 101, 2 and 99 make 101, 3 and 98 make 101, and so on down to 50 and 51. That's 50 pairs of 101, which is 5,050.
The same trick works for any count. For n envelopes the total is n times (n + 1), divided by 2. So 50 envelopes come to 50 times 51 over 2, which is 1,275.
The average envelope holds 50.50. Keep that number in mind, because it's the easiest way to plan your pace.
Smaller and bigger versions
5,050 is a lot of money for many people, so there are a few common ways to scale it. They all keep the same rule, envelope n holds n times what envelope 1 holds, which is also how my app does it. Type the first amount in the tracker above and it does the rest.
| Version | Envelopes | Envelope 1 | Biggest | Total |
|---|---|---|---|---|
| The classic | 100 | 1 | 100 | 5,050 |
| Half amounts | 100 | 0.50 | 50 | 2,525 |
| Double amounts | 100 | 2 | 200 | 10,100 |
| 50 envelopes | 50 | 1 | 50 | 1,275 |
Half amounts means envelope 1 holds 0.50 and envelope 100 holds 50. If you'd rather keep whole numbers, the 50 envelope version is the gentler start. Doubling works too, but the last envelopes get heavy: two big draws in one week can come to almost 400.
How long it takes
The challenge has no fixed length. It depends on how many envelopes you fill each week, and the average envelope tells you roughly what each week costs.
| Pace | Done in | Average a week |
|---|---|---|
| One a day | 100 days | 353.50 |
| Four a week | 25 weeks | 202 |
| Three a week | 34 weeks | 151.50 |
| Two a week | 50 weeks | 101 |
| One a week | 100 weeks | 50.50 |
Those are averages. Real weeks swing a lot. At two envelopes a week you could pull 1 and 2 one week and 99 and 100 another, so a single week can cost anywhere from 3 to 199. Set the Finish by date above and the tracker works out the pace from what you have left.
Can I do it in six months?
Six months is about 26 weeks. 100 envelopes over 26 weeks is close to four a week, and four a week finishes in 25 weeks. On average that's about 202 a week, or around 840 a month. Over a whole year at two a week, it's about 101 a week.
If six months sounds tight, pick half amounts. Same number of envelopes, same pace, half the money.
A few things that help
- Tie it to something you already do, like payday or a Sunday evening.
- Keep the money apart from your spending money. A separate savings account works as well as real envelopes.
- If a big envelope comes up in a tight week, draw again and come back to it later. It's still in the pile.
- Mark it here the same day you save. A chart you update every week is easier to stick with.
None of this is financial advice. It's simple arithmetic plus a habit, and the habit is the hard part.
Printing the chart
Print a blank chart gives you a clean 10 by 10 grid with each envelope's number and amount, nothing crossed off, ready for the fridge. Print my chart does the same with the envelopes you've filled shaded and struck through. Both use whatever first amount and currency you picked, and both fit on one A4 or letter page. To keep a PDF, choose Save as PDF in the print window.
Questions
How much money is the 100 envelope challenge?
5,050 when envelope 1 holds 1. With half amounts it's 2,525, with double amounts 10,100, and the 50 envelope version comes to 1,275.
How long does the 100 envelope challenge take?
That's up to you. One envelope a day takes 100 days, two a week takes 50 weeks, and four a week takes 25 weeks.
Do I need real envelopes?
No. Plenty of people just move the amount into a savings account and cross the envelope off a chart. Real envelopes work well if you're saving cash and like to see it pile up.
Can I pick envelopes instead of drawing at random?
Yes. Tap any envelope you like. Drawing at random keeps you honest, but the total is the same whichever order you fill them in.
Is my progress saved?
Only in this browser on this device. If you clear the site's data or switch phones, the chart starts empty again. The app has backups you can move to a new phone.
Is there a version for my phone?
Yes. My Savings Challenge app for Android has the same 100 envelopes, with a draw button, a jar that fills up and a weekly reminder. It works offline and never connects to your bank.
If you're starting today, draw your first envelope now, even if it's a small one. The second one is always easier.
Savings Challenge
Draw an envelope, tap to save and watch the jar fill, with a weekly reminder and a home screen widget.