See also Investing and Retirement

Common thinking on what you need for retirement in 2015 is $400,000 - $1,000,000 for middle class families. Depending on Social Security and Pension income you may need less. See Retirement.

Inflation 3% (See charts for average inflation)

Savings: - Amount accumulated in portfolio at 7% return. (See charts for average return)

contribution/yr	$10,000	$15,000	$20,000	$25,000	$30,000
25 yrs	$632,490	$948,735	$1,264,980	$1,581,225	$1,897,471
40yrs	$1,996,351	$2,994,526	$3,992,702	$4,990,877	$5,989,053

Of course it's not that simple. Savings and income will vary your life style and age. DINKs (Dual-Income, No Kids) will have a different savings pattern than the average family.

The value of compounding
The take away here is to start saving for retirement as early as you can.
Three hypothetical examples
1. Start early invest for 10 years and let it ride.
2. Wait 10 years and and continue to invest for 20 years.
3. Start early and continue to invest.

Growth Rate=8.00% *

Age	Amount Invested	Total Value	Amount Invested	Total Value	Amount Invested	Total Value
30	$10,000	$10,000			$5,000	$5,000
31	$10,000	$20,800			$5,000	$10,400
32	$10,000	$32,464			$5,000	$16,232
33	$10,000	$45,061			$5,000	$22,531
34	$10,000	$58,666			$5,000	$29,333
35	$10,000	$73,359			$5,000	$36,680
36	$10,000	$89,228			$5,000	$44,614
37	$10,000	$106,366			$5,000	$53,183
38	$10,000	$124,876			$5,000	$62,438
39	$10,000	$144,866			$5,000	$72,433
40		$156,455	$10,000	$10,000	$10,000	$88,227
41		$168,971	$10,000	$20,800	$10,000	$105,286
42		$182,489	$10,000	$32,464	$10,000	$123,708
43		$197,088	$10,000	$45,061	$10,000	$143,605
44		$212,855	$10,000	$58,666	$10,000	$165,094
45		$229,884	$10,000	$73,359	$10,000	$188,301
46		$248,274	$10,000	$89,228	$10,000	$213,365
47		$268,136	$10,000	$106,366	$10,000	$240,434
48		$289,587	$10,000	$124,876	$10,000	$269,669
49		$312,754	$10,000	$144,866	$10,000	$301,243
50		$337,774	$10,000	$166,455	$10,000	$335,342
51		$364,796	$10,000	$189,771	$10,000	$372,169
52		$393,980	$10,000	$214,953	$10,000	$411,943
53		$425,498	$10,000	$242,149	$10,000	$454,898
54		$459,538	$10,000	$271,521	$10,000	$501,290
55		$496,301	$10,000	$303,243	$10,000	$551,393
56		$536,005	$10,000	$337,502	$10,000	$605,505
57		$578,886	$10,000	$374,502	$10,000	$663,945
58		$625,197	$10,000	$414,463	$10,000	$727,061
59		$675,212	$10,000	$457,620	$10,000	$795,226
Total Saved	$100,000		$200,000		$250,000

An excel spread sheet you can use to change the numbers.

* Some fiancial planners still use 10% growth. The 25 year averages are down because of the 2008 recession. See chart below. I think 7 or 8% are more conservative number to use for expected growth.

† - The net present value of $10,000 today is more than $10,000 10-20 years from now, but with current inflation rates < 3% it wasn't worth trying to compensate for that.

See Retirement for how much you need to retire.

In Stein-DeMuth "Yes, You Can Get A Financial Life!", they list the following saving stages.
Figure 7.3: Recommended Annual Contributions to our Withdrawls from Savings for One-Child, Median-Income Family to Maintain an Even Lifestyle when Buying a House.

They say you would spend most of your savings on a house at age 35, then start saving for retirement. They will bump up retirement savings at age 50 when kids are gone.
In a email to me, DeMuth said the above assumed that Social Security was going to provide a significant part of your retirement income so you could put off savings.
He said however, you should always take full advantage of retirement savings accounts at any age: capturing 401k employer matches and funding IRAs/401ks (or Roth IRAs/Roth 401ks) to the limit -- even at the expense of postponing a home purchase or having children. The tax-deduction and long-term tax-free compounding is hard to beat.

According to Strutt & Parker’s list, 
Giving up one night out a week could save a couple, $8,000  per year.
 Eliminating takeout meals could save $3,500 
Bringing lunch from home —  could tack on an additional $3,400 
Forgoing an annual vacation - $900
Lottery tickets   - $1,100
annual phone upgrade - $200
Totaling $84,000 over 5 years

Consumer Reports says people with between $400,000 and $1 million in savings were just as happy as those with more. See retirement.

In the Stein-DeMuth book (above) they list the saving progress chart below.
It assumes you start saving in your early 20s and retire at 70 with no social security or pension, live on 80% of your pre-retirement income and live to 100. % of current salary going to savings.
Multiple of Current Salary You Should Have in Savings

Risk	Age 25	Age 30	Age 35	Age 40	Age 45	Age 50	Age 55	Age 60	Age 65	Age 70
Conservative	0.1	0.4	1	1.6	2.6	4	5.9	8.7	12.1	16
Moderate	0.05	0.33	0.7	1.2	2	3.1	4.7	7.1	9.9	13.1

Conservative plan would take you to age 105, Moderate to age 100.

You should always be saving the maximum amount from all tax-advantaged, employer-subsidized savings plans, such as Keogh and 401(k)s.

The Social Security (SS) Cost-of-Living Adjustment (COLA) is tied to the Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W). For the last 20 years it has been pretty close to the regular CPI. See Social Security COLA in Retirement.
and See: Consumer Price Index For Urban Wage Earners And Clerical Workers (CPI-W) | Investopedia
and Social Security Benefits Rising 1.7% For 2015, Top Tax Up 1.3% - Forbes

While advocates for the elderly argue CPI-W understates the true increase in costs the elderly face, deficit hawks have pushed for linking COLAs to an even lower measure of inflation known as the chained CPI.