Retirement Pension calculation

Calculation of how much you need  to save for pension  is not magic. It can be expressed by a simple equation like this:

Assuming 4% inflation*
and your current monthly expenditure is 1 lakh.
for calculating life expetency you can refer:
https://twitter.com/srikundansingh/status/1147423727753187328

This is table for monthly saving you need:

Current Age	Retirement Age	life expectancy	Interest rate %	Monthly saving needed
30	40	80	6	612216
30	40	80	8	443951
30	40	80	10	333052
30	40	80	12	255669
30	40	90	6	962869
30	40	90	8	690015
30	40	90	10	513540
30	40	90	12	391969
30	40	100	6	1487250
30	40	100	8	1056611
30	40	100	10	781885
30	40	100	12	594362
30	40	110	6	2272055
30	40	110	8	1603538
30	40	110	10	1181492
30	40	110	12	895401
30	45	80	6	331079
30	45	80	8	226990
30	45	80	10	160033
30	45	80	12	114896
30	45	90	6	527922
30	45	90	8	356871
30	45	90	10	249194
30	45	90	12	177667
30	45	100	6	821839
30	45	100	8	549996
30	45	100	10	381479
30	45	100	12	270681
30	45	110	6	1261662
30	45	110	8	838003
30	45	110	10	578371
30	45	110	12	408953
30	50	80	6	197756
30	50	80	8	127749
30	50	80	10	84228
30	50	80	12	56221
30	50	90	6	321426
30	50	90	8	204108
30	50	90	10	132989
30	50	90	12	88004
30	50	100	6	505527
30	50	100	8	317237
30	50	100	10	205060
30	50	100	12	134920
30	50	110	6	780838
30	50	110	8	485781
30	50	110	10	312211
30	50	110	12	204586
30	55	80	6	123060
30	55	80	8	74726
30	55	80	10	45909
30	55	80	12	28368
30	55	90	6	205664
30	55	90	8	122256
30	55	90	10	73998
30	55	90	12	45222
30	55	100	6	327941
30	55	100	8	192210
30	55	100	10	115225
30	55	100	12	69928
30	55	110	6	510520
30	55	110	8	296227
30	55	110	10	176392
30	55	110	12	106538
30	60	80	6	77178
30	60	80	8	44016
30	60	80	10	25150
30	60	80	12	14353
30	60	90	6	134644
30	60	90	8	74736
30	60	90	10	41883
30	60	90	12	23556
30	60	100	6	218846
30	60	100	8	119408
30	60	100	10	66130
30	60	100	12	36872
30	60	110	6	344192
30	60	110	8	185591
30	60	110	10	101968
30	60	110	12	56529
30	65	80	6	47256
30	65	80	8	25348
30	65	80	10	13477
30	65	80	12	7104
30	65	90	6	88604
30	65	90	8	45859
30	65	90	10	23749
30	65	90	12	12268
30	65	100	6	148079
30	65	100	8	75028
30	65	100	10	38279
30	65	100	12	19557
30	65	110	6	236119
30	65	110	8	117959
30	65	110	10	59607
30	65	110	12	30241
30	70	80	6	26763
30	70	80	8	13571
30	70	80	10	6742
30	70	80	12	3294
30	70	90	6	57624
30	70	90	8	27815
30	70	90	10	13307
30	70	90	12	6311
30	70	100	6	100530
30	70	100	8	47228
30	70	100	10	22160
30	70	100	12	10358
30	70	110	6	163399
30	70	110	8	75458
30	70	110	10	34989
30	70	110	12	16214
35	45	80	6	482907
35	45	80	8	352892
35	45	80	10	266140
35	45	80	12	205090
35	45	90	6	770019
35	45	90	8	554812
35	45	90	10	414418
35	45	90	12	317136
35	45	100	6	1198721
35	45	100	8	855055
35	45	100	10	634413
35	45	100	12	483166
35	45	110	6	1840241
35	45	110	8	1302807
35	45	110	10	961852
35	45	110	12	729980
35	50	80	6	258239
35	50	80	8	178730
35	50	80	10	126837
35	50	80	12	91503
35	50	90	6	419733
35	50	90	8	285562
35	50	90	10	200267
35	50	90	12	143232
35	50	100	6	660139
35	50	100	8	443837
35	50	100	10	308797
35	50	100	12	219591
35	50	110	6	1019653
35	50	110	8	679643
35	50	110	10	470155
35	50	110	12	332976
35	55	80	6	151705
35	55	80	8	99167
35	55	80	10	65932
35	55	80	12	44284
35	55	90	6	253536
35	55	90	8	162244
35	55	90	10	106271
35	55	90	12	70594
35	55	100	6	404276
35	55	100	8	255077
35	55	100	10	165479
35	55	100	12	109162
35	55	110	6	629354
35	55	110	8	393115
35	55	110	10	253325
35	55	110	12	166311
35	60	80	6	91951
35	60	80	8	56695
35	60	80	10	35218
35	60	80	12	21945
35	60	90	6	160416
35	60	90	8	96264
35	60	90	10	58648
35	60	90	12	36015
35	60	100	6	260735
35	60	100	8	153803
35	60	100	10	92602
35	60	100	12	56375
35	60	110	6	410074
35	60	110	8	239050
35	60	110	10	142785
35	60	110	12	86429
35	65	80	6	55088
35	65	80	8	32067
35	65	80	10	18605
35	65	80	12	10744
35	65	90	6	103290
35	65	90	8	58015
35	65	90	10	32785
35	65	90	12	18554
35	65	100	6	172622
35	65	100	8	94916
35	65	100	10	52844
35	65	100	12	29578
35	65	110	6	275255
35	65	110	8	149226
35	65	110	10	82286
35	65	110	12	45737
35	70	80	6	30749
35	70	80	8	16976
35	70	80	10	9231
35	70	80	12	4954
35	70	90	6	66205
35	70	90	8	34793
35	70	90	10	18218
35	70	90	12	9490
35	70	100	6	115500
35	70	100	8	59077
35	70	100	10	30339
35	70	100	12	15575
35	70	110	6	187731
35	70	110	8	94388
35	70	110	10	47904
35	70	110	12	24380
40	50	80	6	376663
40	50	80	8	277865
40	50	80	10	210936
40	50	80	12	163334
40	50	90	6	612216
40	50	90	8	443951
40	50	90	10	333052
40	50	90	12	255669
40	50	100	6	962869
40	50	100	8	690015
40	50	100	10	513540
40	50	100	12	391969
40	50	110	6	1487250
40	50	110	8	1056611
40	50	110	10	781885
40	50	110	12	594362
40	55	80	6	198103
40	55	80	8	138742
40	55	80	10	99287
40	55	80	12	72075
40	55	90	6	331079
40	55	90	8	226990
40	55	90	10	160033
40	55	90	12	114896
40	55	100	6	527922
40	55	100	8	356871
40	55	100	10	249194
40	55	100	12	177667
40	55	110	6	821839
40	55	110	8	549996
40	55	110	10	381479
40	55	110	12	270681
40	60	80	6	113355
40	60	80	8	75238
40	60	80	10	50579
40	60	80	12	34257
40	60	90	6	197756
40	60	90	8	127749
40	60	90	10	84228
40	60	90	12	56221
40	60	100	6	321426
40	60	100	8	204108
40	60	100	10	132989
40	60	100	12	88004
40	60	110	6	505527
40	60	110	8	317237
40	60	110	10	205060
40	60	110	12	134920
40	65	80	6	65633
40	65	80	8	41303
40	65	80	10	26052
40	65	80	12	16426
40	65	90	6	123060
40	65	90	8	74726
40	65	90	10	45909
40	65	90	12	28368
40	65	100	6	205664
40	65	100	8	122256
40	65	100	10	73998
40	65	100	12	45222
40	65	110	6	327941
40	65	110	8	192210
40	65	110	10	115225
40	65	110	12	69928
40	70	80	6	35845
40	70	80	8	21475
40	70	80	10	12743
40	70	80	12	7492
40	70	90	6	77178
40	70	90	8	44016
40	70	90	10	25150
40	70	90	12	14353
40	70	100	6	134644
40	70	100	8	74736
40	70	100	10	41883
40	70	100	12	23556
40	70	110	6	218846
40	70	110	8	119408
40	70	110	10	66130
40	70	110	12	36872
45	55	80	6	288950
45	55	80	8	215696
45	55	80	10	165118
45	55	80	12	128655
45	55	90	6	482907
45	55	90	8	352892
45	55	90	10	266140
45	55	90	12	205090
45	55	100	6	770019
45	55	100	8	554812
45	55	100	10	414418
45	55	100	12	317136
45	55	110	6	1198721
45	55	110	8	855055
45	55	110	10	634413
45	55	110	12	483166
45	60	80	6	148024
45	60	80	8	105264
45	60	80	10	76166
45	60	80	12	55756
45	60	90	6	258239
45	60	90	8	178730
45	60	90	10	126837
45	60	90	12	91503
45	60	100	6	419733
45	60	100	8	285562
45	60	100	10	200267
45	60	100	12	143232
45	60	110	6	660139
45	60	110	8	443837
45	60	110	10	308797
45	60	110	12	219591
45	65	80	6	80910
45	65	80	8	54813
45	65	80	10	37415
45	65	80	12	25643
45	65	90	6	151705
45	65	90	8	99167
45	65	90	10	65932
45	65	90	12	44284
45	65	100	6	253536
45	65	100	8	162244
45	65	100	10	106271
45	65	100	12	70594
45	65	110	6	404276
45	65	110	8	255077
45	65	110	10	165479
45	65	110	12	109162
45	70	80	6	42706
45	70	80	8	27661
45	70	80	10	17844
45	70	80	12	11456
45	70	90	6	91951
45	70	90	8	56695
45	70	90	10	35218
45	70	90	12	21945
45	70	100	6	160416
45	70	100	8	96264
45	70	100	10	58648
45	70	100	12	36015
45	70	110	6	260735
45	70	110	8	153803
45	70	110	10	92602
45	70	110	12	56375	This			t

The saving number is just a multiplication factor. Suppose your monthly expenditure is 50,000 then you can divide by 2 to calculate your saving needed.
e.g. your age is 40, wants to be retired at 55 and life expectancy is 90 and interest rate is 8%,
then according to this table you need 2,26,990 for current monthly expenditure of 1 lakh.
for 50,000 current expenditure , your monthly savings need to be: 226990/2 = 113495 only.

* this happened only twice in Bharat 1998-2004 and 2014-2019. rest of time it was much higher( close to 8%)