Free tool · no signup

One reservation of this size covers what, exactly?

Pick a service, a family, and a size, and see the exact AWS normalization units behind it: how many smaller sizes it equals, the RDS Multi-AZ factor, and where the rule stops applying. Every number is sourced, not estimated.

The calculator

Pick a reservation. See its ladder.

ServiceFamilySizeDeploymentMulti-AZ

db.r6g.xlarge carries 8 normalized units.See its full price page →

1× xlarge
2× large
4× medium
8× small
16× micro
32× nano

This ladder shows AWS's own normalization units, sourced from the same table Reserver's own coverage matcher uses. It is not a guarantee your account owns a reservation this size, only what one of this size would equal.

The full table

Every AWS size, one normalization factor each.

This is the exact table behind the ladder above and behind Reserver's own coverage matcher. A large-family jump (2xlarge to 3xlarge, for example) is not always a clean double: read the units column, not the size name, for the real ratio.

AWS Reserved Instance normalization units by size
Size	Normalized units
nano	0.25
micro	0.5
small	1
medium	2
large	4
xlarge	8
2xlarge	16
3xlarge	24
4xlarge	32
6xlarge	48
8xlarge	64
9xlarge	72
10xlarge	80
12xlarge	96
16xlarge	128
18xlarge	144
24xlarge	192
32xlarge	256
48xlarge	384
56xlarge	448
96xlarge	768
112xlarge	896

A *.metal size is not on this scale (see "Where it does not apply" below), but AWS still publishes a units figure for the families it sells bare metal in:

AWS bare-metal normalization units by family
Family	Normalized units (.metal)
a1.metal	32
m5zn.metal	96
x2iezn.metal	96
z1d.metal	96
c6g.metal	128
c6gd.metal	128
i3.metal	128
m6g.metal	128
m6gd.metal	128
r6g.metal	128
r6gd.metal	128
x2gd.metal	128
c5n.metal	144
c5.metal	192
c5d.metal	192
i3en.metal	192
m5.metal	192
m5d.metal	192
m5dn.metal	192
m5n.metal	192
r5.metal	192
r5b.metal	192
r5d.metal	192
r5dn.metal	192
r5n.metal	192
c6i.metal	256
c6id.metal	256
m6i.metal	256
m6id.metal	256
r6d.metal	256
r6id.metal	256
r6i.metal	256
u-18tb1.metal	448
u-24tb1.metal	448
u-6tb1.metal	896
u-9tb1.metal	896
u-12tb1.metal	896

Read this first

Where size flexibility does not apply.

A regional EC2 Reserved Instance, Linux/UNIXFlexes: Flexes across every size in its family, region-wide.
A regional EC2 Reserved Instance, WindowsDoes not flex: EC2 size flexibility applies to Linux/UNIX only.
A zonal EC2 Reserved InstanceDoes not flex: Size flexibility applies to regional scope only. A zonal RI is pinned to one Availability Zone and one size.
An RDS Reserved Instance, PostgreSQLFlexes: RDS flexes across sizes for every engine except SQL Server and Oracle.
An RDS Reserved Instance, SQL ServerDoes not flex: RDS size flexibility excludes SQL Server, standard or RDS Custom.
An RDS Reserved Instance, OracleDoes not flex: RDS size flexibility excludes Oracle too, standard or RDS Custom, License Included or BYOL.
An ElastiCache Reserved InstanceFlexes: Flexes across sizes within the same family, region, and engine, for every reservation bought since 1 October 2024.

One rule holds across every service: size flexibility never crosses an instance family. An r6g reservation covers r6g instances of any eligible size, in that region. It never covers an m6g instance, whatever the two families' units say.

ElastiCache Valkey is one more edge case worth naming. AWS publishes a separate, lower normalization table for Valkey, about 0.8 times the figures above. A reservation only ever covers instances running its own engine, so that separate table cancels out on both sides of the comparison and never changes what a Valkey reservation actually covers.

Built for your size

The right size pays off at every fleet size.

Startup1–10 reservations · a single account

The right size still saves about $10,530 a year here. A renewal missed by 14 days would cost about $92.

Growthdozens of reservations · a few accounts

The right size still saves about $105,300 a year here. A renewal missed by 14 days would cost about $951.

Enterprisehundreds to thousands · many AWS accounts & orgs

The right size still saves about $1,053,000 a year here. A renewal missed by 14 days would cost about $6,904.

One thing this does not change

Flexibility does not extend the term.

A size-flexible reservation still expires on the exact date you bought it for. Flexibility changes what it covers while it is active. It does not add a single day to how long it stays active. Track your real expiry dates with the free Expiry Check, or see what a missed renewal costs your whole fleet with the renewal exposure calculator.

Size flexibility, answered

Questions about the calculator.

Does size flexibility work the same way for RDS, ElastiCache, and EC2?

No. Each service sells different sizes, but every service reads the same AWS normalization-factor numbers shown on this page. An xlarge is worth 8 units and a large is worth 4 units, in RDS, ElastiCache, and EC2 alike. What differs is eligibility: EC2 needs Linux/UNIX, RDS excludes SQL Server and Oracle, and ElastiCache has covered every engine since 1 October 2024. See "Where size flexibility does not apply" below.

Does a Multi-AZ RDS reservation cover more than a Single-AZ one?

Yes. A Multi-AZ reservation carries twice the normalized units of the same size bought Single-AZ. Toggle Multi-AZ above to see the doubled ladder for your selected size.

Can one reservation cover an instance in a different family?

No, never. Size flexibility only ever moves between sizes inside one family. An r6g reservation covers r6g instances of any size in its region, but it never covers an m6g instance, a c6g instance, or any size of any other family, no matter how the units line up.

Does size flexibility extend how long my reservation lasts?

No. A size-flexible reservation still expires on the exact date you bought it for. Flexibility changes what it covers while it's active, not how long it stays active. Track your own expiry dates with the free Expiry Check, or read the renewal exposure calculator for what a missed renewal costs at your fleet size.

Reviewed Sep 4, 2026