diff --git a/cli/cli_progress.go b/cli/cli_progress.go
index 7dcaafbdb..791f6a465 100644
--- a/cli/cli_progress.go
+++ b/cli/cli_progress.go
@@ -47,8 +47,8 @@ type cliProgress struct {
 	spinPhase       int
 	uploadStartTime time.Time
 
-	previousFileCount int
-	previousTotalSize int64
+	estimatedFileCount  int
+	estimatedTotalBytes int64
 
 	// indicates shared instance that does not reset counters at the beginning of upload.
 	shared bool
@@ -152,13 +152,29 @@ func (p *cliProgress) output(col *color.Color, msg string) {
 		return
 	}
 
-	if p.previousTotalSize > 0 {
-		percent := (float64(hashedBytes+cachedBytes) * hundredPercent / float64(p.previousTotalSize))
-		if percent > hundredPercent {
-			percent = hundredPercent
+	if p.estimatedTotalBytes > 0 {
+		line += fmt.Sprintf(", estimated %v", units.BytesStringBase10(p.estimatedTotalBytes))
+
+		ratio := float64(hashedBytes+cachedBytes) / float64(p.estimatedTotalBytes)
+		if ratio > 1 {
+			ratio = 1
 		}
 
-		line += fmt.Sprintf(" %.1f%%", percent)
+		timeSoFarSeconds := clock.Since(p.uploadStartTime).Seconds()
+		estimatedTotalTime := time.Second * time.Duration(timeSoFarSeconds/ratio)
+		estimatedEndTime := p.uploadStartTime.Add(estimatedTotalTime)
+
+		remaining := clock.Until(estimatedEndTime)
+		if remaining < 0 {
+			remaining = 0
+		}
+
+		remaining = remaining.Round(time.Second)
+
+		line += fmt.Sprintf(" (%.1f%%)", ratio*hundredPercent)
+		line += fmt.Sprintf(" %v left", remaining)
+	} else {
+		line += ", estimating..."
 	}
 
 	var extraSpaces string
@@ -197,20 +213,31 @@ func (p *cliProgress) FinishShared() {
 	p.output(defaultColor, "")
 }
 
-func (p *cliProgress) UploadStarted(previousFileCount int, previousTotalSize int64) {
+func (p *cliProgress) UploadStarted() {
 	if p.shared {
 		// do nothing
 		return
 	}
 
 	*p = cliProgress{
-		uploading:         1,
-		uploadStartTime:   clock.Now(),
-		previousFileCount: previousFileCount,
-		previousTotalSize: previousTotalSize,
+		uploading:       1,
+		uploadStartTime: clock.Now(),
 	}
 }
 
+func (p *cliProgress) EstimatedDataSize(fileCount int, totalBytes int64) {
+	if p.shared {
+		// do nothing
+		return
+	}
+
+	p.outputMutex.Lock()
+	defer p.outputMutex.Unlock()
+
+	p.estimatedFileCount = fileCount
+	p.estimatedTotalBytes = totalBytes
+}
+
 func (p *cliProgress) UploadFinished() {
 	// do nothing here, we still want to report the files flushed after the Upload has completed.
 	// instead, Finish() will be called.
diff --git a/htmlui/src/SourcesTable.js b/htmlui/src/SourcesTable.js
index a138e4c62..5a345060d 100644
--- a/htmlui/src/SourcesTable.js
+++ b/htmlui/src/SourcesTable.js
@@ -203,8 +203,10 @@ export class SourcesTable extends Component {
                     const totalBytes = u.hashedBytes + u.cachedBytes;
 
                     totals = sizeDisplayName(totalBytes);
-                    if (x.row.original.lastSnapshot) {
-                        const percent = Math.round(totalBytes * 1000.0 / x.row.original.lastSnapshot.stats.totalSize) / 10.0;
+                    if (u.estimatedBytes) {
+                        totals += "/" + sizeDisplayName(u.estimatedBytes);
+
+                        const percent = Math.round(totalBytes * 1000.0 / u.estimatedBytes) / 10.0;
                         if (percent <= 100) {
                             totals += " " + percent + "%";
                         }
@@ -212,7 +214,7 @@ export class SourcesTable extends Component {
                 }
 
                 return <>
-                    <Spinner animation="border" variant="primary" size="sm" title={title} />&nbsp;Snapshotting {totals}
+                    <Spinner animation="border" variant="primary" size="sm" title={title} />&nbsp;Uploading {totals}
                     &nbsp;
                     <Button variant="danger" size="sm" onClick={() => {
                         parent.cancelSnapshot(x.row.original.source);
diff --git a/snapshot/snapshotfs/upload.go b/snapshot/snapshotfs/upload.go
index d1f8b5cd1..b84a353bc 100644
--- a/snapshot/snapshotfs/upload.go
+++ b/snapshot/snapshotfs/upload.go
@@ -78,6 +78,9 @@ type Uploader struct {
 
 	// for testing only, when set will write to a given channel whenever checkpoint completes
 	checkpointFinished chan struct{}
+
+	// disable snapshot size estimation
+	disableEstimation bool
 }
 
 // IsCanceled returns true if the upload is canceled.
@@ -694,6 +697,7 @@ func (u *Uploader) processNonDirectories(ctx context.Context, parentCheckpointRe
 		// See if we had this name during either of previous passes.
 		if cachedEntry := u.maybeIgnoreCachedEntry(ctx, findCachedEntry(ctx, entry, prevEntries)); cachedEntry != nil {
 			atomic.AddInt32(&u.stats.CachedFiles, 1)
+			atomic.AddInt64(&u.stats.TotalFileSize, entry.Size())
 			u.Progress.CachedFile(filepath.Join(dirRelativePath, entry.Name()), entry.Size())
 
 			// compute entryResult now, cachedEntry is short-lived
@@ -943,20 +947,8 @@ func (u *Uploader) Upload(
 		Source: sourceInfo,
 	}
 
-	maxPreviousTotalFileSize := int64(0)
-	maxPreviousFileCount := 0
+	u.Progress.UploadStarted()
 
-	for _, m := range previousManifests {
-		if s := m.Stats.TotalFileSize; s > maxPreviousTotalFileSize {
-			maxPreviousTotalFileSize = s
-		}
-
-		if s := int(m.Stats.TotalFileCount); s > maxPreviousFileCount {
-			maxPreviousFileCount = s
-		}
-	}
-
-	u.Progress.UploadStarted(maxPreviousFileCount, maxPreviousTotalFileSize)
 	defer u.Progress.UploadFinished()
 
 	u.stats = snapshot.Stats{}
@@ -966,6 +958,9 @@ func (u *Uploader) Upload(
 
 	s.StartTime = u.repo.Time()
 
+	scanctx, cancelScan := context.WithCancel(ctx)
+	defer cancelScan()
+
 	switch entry := source.(type) {
 	case fs.Directory:
 		var previousDirs []fs.Directory
@@ -979,9 +974,17 @@ func (u *Uploader) Upload(
 		entry = ignorefs.New(entry, policyTree, ignorefs.ReportIgnoredFiles(func(_ string, md fs.Entry) {
 			u.stats.AddExcluded(md)
 		}))
+
+		go func() {
+			ds, _ := u.scanDirectory(scanctx, entry)
+
+			u.Progress.EstimatedDataSize(ds.numFiles, ds.totalFileSize)
+		}()
+
 		s.RootEntry, err = u.uploadDirWithCheckpointing(ctx, entry, policyTree, previousDirs, sourceInfo)
 
 	case fs.File:
+		u.Progress.EstimatedDataSize(1, entry.Size())
 		s.RootEntry, err = u.uploadFileWithCheckpointing(ctx, entry.Name(), entry, policyTree.EffectivePolicy(), sourceInfo)
 
 	default:
diff --git a/snapshot/snapshotfs/upload_progress.go b/snapshot/snapshotfs/upload_progress.go
index 6cc8cb1dc..0c383a17b 100644
--- a/snapshot/snapshotfs/upload_progress.go
+++ b/snapshot/snapshotfs/upload_progress.go
@@ -8,7 +8,7 @@
 // UploadProgress is invoked by by uploader to report status of file and directory uploads.
 type UploadProgress interface {
 	// UploadStarted is emitted once at the start of an upload
-	UploadStarted(previousFileCount int, previousTotalSize int64)
+	UploadStarted()
 
 	// UploadFinished is emitted once at the end of an upload
 	UploadFinished()
@@ -36,6 +36,9 @@ type UploadProgress interface {
 
 	// FinishedDirectory is emitted whenever a directory is finished uploading.
 	FinishedDirectory(dirname string)
+
+	// EstimatedDataSize is emitted whenever the size of upload is estimated.
+	EstimatedDataSize(fileCount int, totalBytes int64)
 }
 
 // NullUploadProgress is an implementation of UploadProgress that does not produce any output.
@@ -43,7 +46,10 @@ type NullUploadProgress struct {
 }
 
 // UploadStarted implements UploadProgress.
-func (p *NullUploadProgress) UploadStarted(previousFileCount int, previousTotalSize int64) {}
+func (p *NullUploadProgress) UploadStarted() {}
+
+// EstimatedDataSize implements UploadProgress.
+func (p *NullUploadProgress) EstimatedDataSize(fileCount int, totalBytes int64) {}
 
 // UploadFinished implements UploadProgress.
 func (p *NullUploadProgress) UploadFinished() {}
@@ -79,10 +85,13 @@ type UploadCounters struct {
 	TotalCachedBytes int64 `json:"cachedBytes"`
 	TotalHashedBytes int64 `json:"hashedBytes"`
 
+	EstimatedBytes int64 `json:"estimatedBytes"`
+
 	TotalCachedFiles int32 `json:"cachedFiles"`
 	TotalHashedFiles int32 `json:"hashedFiles"`
 
 	TotalIgnoredErrors int32 `json:"ignoredErrors"`
+	EstimatedFiles     int32 `json:"estimatedFiles"`
 
 	CurrentDirectory string `json:"directory"`
 
@@ -100,11 +109,17 @@ type CountingUploadProgress struct {
 }
 
 // UploadStarted implements UploadProgress.
-func (p *CountingUploadProgress) UploadStarted(previousFileCount int, previousTotalFileSize int64) {
+func (p *CountingUploadProgress) UploadStarted() {
 	// reset counters to all-zero values.
 	p.counters = UploadCounters{}
 }
 
+// EstimatedDataSize implements UploadProgress.
+func (p *CountingUploadProgress) EstimatedDataSize(numFiles int, numBytes int64) {
+	atomic.StoreInt64(&p.counters.EstimatedBytes, numBytes)
+	atomic.StoreInt32(&p.counters.EstimatedFiles, int32(numFiles))
+}
+
 // HashedBytes implements UploadProgress.
 func (p *CountingUploadProgress) HashedBytes(numBytes int64) {
 	atomic.AddInt64(&p.counters.TotalHashedBytes, numBytes)
@@ -149,6 +164,8 @@ func (p *CountingUploadProgress) Snapshot() UploadCounters {
 		TotalHashedFiles: atomic.LoadInt32(&p.counters.TotalHashedFiles),
 		TotalCachedBytes: atomic.LoadInt64(&p.counters.TotalCachedBytes),
 		TotalHashedBytes: atomic.LoadInt64(&p.counters.TotalHashedBytes),
+		EstimatedBytes:   atomic.LoadInt64(&p.counters.EstimatedBytes),
+		EstimatedFiles:   atomic.LoadInt32(&p.counters.EstimatedFiles),
 		CurrentDirectory: p.counters.CurrentDirectory,
 		LastErrorPath:    p.counters.LastErrorPath,
 		LastError:        p.counters.LastError,
diff --git a/snapshot/snapshotfs/upload_scan.go b/snapshot/snapshotfs/upload_scan.go
new file mode 100644
index 000000000..8dfa1f722
--- /dev/null
+++ b/snapshot/snapshotfs/upload_scan.go
@@ -0,0 +1,51 @@
+package snapshotfs
+
+import (
+	"context"
+
+	"github.com/kopia/kopia/fs"
+)
+
+type scanResults struct {
+	numFiles      int
+	totalFileSize int64
+}
+
+// scanDirectory computes the number of files and their total size in a given directory recursively descending
+// into subdirectories. The scan teminates early as soon as the provided context is canceled.
+func (u *Uploader) scanDirectory(ctx context.Context, dir fs.Directory) (scanResults, error) {
+	var res scanResults
+
+	if u.disableEstimation {
+		return res, nil
+	}
+
+	entries, err := dir.Readdir(ctx)
+	if err != nil {
+		return res, err
+	}
+
+	for _, e := range entries {
+		if err := ctx.Err(); err != nil {
+			// terminate early if context got canceled
+			return res, err
+		}
+
+		switch e := e.(type) {
+		case fs.Directory:
+			dr, err := u.scanDirectory(ctx, e)
+			res.numFiles += dr.numFiles
+			res.totalFileSize += dr.totalFileSize
+
+			if err != nil {
+				return res, err
+			}
+
+		case fs.File:
+			res.numFiles++
+			res.totalFileSize += e.Size()
+		}
+	}
+
+	return res, nil
+}
diff --git a/snapshot/snapshotfs/upload_test.go b/snapshot/snapshotfs/upload_test.go
index c25787a14..375ee1080 100644
--- a/snapshot/snapshotfs/upload_test.go
+++ b/snapshot/snapshotfs/upload_test.go
@@ -299,6 +299,7 @@ func TestUploadWithCheckpointing(t *testing.T) {
 
 	// create a channel that will be sent to whenever checkpoint completes.
 	u.checkpointFinished = make(chan struct{})
+	u.disableEstimation = true
 
 	policyTree := policy.BuildTree(nil, policy.DefaultPolicy)