diff --git a/cli/params.go b/cli/params.go
index df7e240ec..11a956120 100644
--- a/cli/params.go
+++ b/cli/params.go
@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"github.com/docker/go-units"
 	"github.com/filecoin-project/lotus/build"
 	"golang.org/x/xerrors"
 	"gopkg.in/urfave/cli.v2"
@@ -10,13 +11,18 @@ var fetchParamCmd = &cli.Command{
 	Name:  "fetch-params",
 	Usage: "Fetch proving parameters",
 	Flags: []cli.Flag{
-		&cli.Uint64Flag{
+		&cli.StringFlag{
 			Name:  "proving-params",
-			Usage: "download params used creating proofs for given size",
+			Usage: "download params used creating proofs for given size, i.e. 32GiB",
 		},
 	},
 	Action: func(cctx *cli.Context) error {
-		err := build.GetParams(cctx.Uint64("proving-params"))
+		sectorSizeInt, err := units.FromHumanSize(cctx.String("proving-params"))
+		if err != nil {
+			return err
+		}
+		sectorSize := uint64(sectorSizeInt)
+		err = build.GetParams(sectorSize)
 		if err != nil {
 			return xerrors.Errorf("fetching proof parameters: %w", err)
 		}
diff --git a/cmd/lotus-bench/main.go b/cmd/lotus-bench/main.go
index 7964186f2..b94cb8fa0 100644
--- a/cmd/lotus-bench/main.go
+++ b/cmd/lotus-bench/main.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"crypto/sha256"
 	"fmt"
+	"github.com/docker/go-units"
 	"io/ioutil"
 	"math/rand"
 	"os"
@@ -60,9 +61,10 @@ func main() {
 				Value: "~/.lotus-bench",
 				Usage: "Path to the storage directory that will store sectors long term",
 			},
-			&cli.Uint64Flag{
+			&cli.StringFlag{
 				Name:  "sector-size",
-				Value: 1024,
+				Value: "1GiB",
+				Usage: "size of the sectors in bytes, i.e. 32GiB",
 			},
 			&cli.BoolFlag{
 				Name:  "no-gpu",
@@ -95,7 +97,11 @@ func main() {
 				return err
 			}
 
-			sectorSize := c.Uint64("sector-size")
+			sectorSizeInt, err := units.FromHumanSize(c.String("sector-size"))
+			if err != nil {
+				return err
+			}
+			sectorSize := uint64(sectorSizeInt)
 
 			mds := datastore.NewMapDatastore()
 			cfg := &sectorbuilder.Config{
diff --git a/go.mod b/go.mod
index 32b469d60..b6d315e20 100644
--- a/go.mod
+++ b/go.mod
@@ -8,6 +8,7 @@ require (
 	github.com/GeertJohan/go.rice v1.0.0
 	github.com/Gurpartap/async v0.0.0-20180927173644-4f7f499dd9ee
 	github.com/StackExchange/wmi v0.0.0-20190523213315-cbe66965904d // indirect
+	github.com/docker/go-units v0.4.0
 	github.com/fatih/color v1.7.0 // indirect
 	github.com/filecoin-project/chain-validation v0.0.3
 	github.com/filecoin-project/filecoin-ffi v0.0.0-20191204125133-ebb3e13addf1
diff --git a/go.sum b/go.sum
index c6c110dab..057e138a0 100644
--- a/go.sum
+++ b/go.sum
@@ -68,6 +68,8 @@ github.com/dgraph-io/badger v1.6.0-rc1/go.mod h1:zwt7syl517jmP8s94KqSxTlM6IMsdhY
 github.com/dgryski/go-farm v0.0.0-20190104051053-3adb47b1fb0f/go.mod h1:SqUrOPUnsFjfmXRMNPybcSiG0BgUW2AuFH8PAnS2iTw=
 github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2 h1:tdlZCpZ/P9DhczCTSixgIKmwPv6+wP5DGjqLYw5SUiA=
 github.com/dgryski/go-farm v0.0.0-20190423205320-6a90982ecee2/go.mod h1:SqUrOPUnsFjfmXRMNPybcSiG0BgUW2AuFH8PAnS2iTw=
+github.com/docker/go-units v0.4.0 h1:3uh0PgVws3nIA0Q+MwDC8yjEPf9zjRfZZWXZYDct3Tw=
+github.com/docker/go-units v0.4.0/go.mod h1:fgPhTUdO+D/Jk86RDLlptpiXQzgHJF7gydDDbaIK4Dk=
 github.com/dustin/go-humanize v1.0.0 h1:VSnTsYCnlFHaM2/igO1h6X3HA71jcobQuxemgkq4zYo=
 github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
 github.com/eapache/go-resiliency v1.1.0/go.mod h1:kFI+JgMyC7bLPUVY133qvEBtVayf5mFgVsvEsIPBvNs=