FUMBX vs. FIBUX

Last updated Jun 3, 2026

FUMBX (Fidelity Short-Term Treasury Bond Index Fund) and FIBUX (Fidelity Flex U.S. Bond Index Fund) are both mutual funds - FUMBX is a Government Bonds fund tracking the Bloomberg Barclays 1-5 Year U.S. Treasury Index, while FIBUX is a Total Bond Market fund managed by Fidelity. Over the past 5 years, FUMBX returned 1.29%/yr vs 0.05%/yr for FIBUX. Their correlation of 0.82 suggests significant overlap in exposure. FUMBX charges 0.03%/yr vs 0.00%/yr for FIBUX.

Performance

FUMBX vs. FIBUX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity Short-Term Treasury Bond Index Fund (FUMBX) and Fidelity Flex U.S. Bond Index Fund (FIBUX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, FUMBX achieves a 0.19% return, which is significantly lower than FIBUX's 0.46% return.

FUMBX

• 1D: -0.10%
• 1M: -0.13%
• YTD: 0.19%
• 6M: 0.46%
• 1Y: 3.39%
• 3Y*: 4.03%
• 5Y*: 1.29%
• 10Y*: —

FIBUX

• 1D: -0.11%
• 1M: 0.13%
• YTD: 0.46%
• 6M: 0.44%
• 1Y: 5.40%
• 3Y*: 4.04%
• 5Y*: 0.05%
• 10Y*: —

*Multi-year figures are annualized to reflect compound growth (CAGR)

FUMBX vs. FIBUX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
FUMBX Fidelity Short-Term Treasury Bond Index Fund	0.19%	5.83%	3.25%	4.47%	-5.84%	-1.38%	4.22%	4.19%	1.47%	-0.33%
FIBUX Fidelity Flex U.S. Bond Index Fund	0.46%	7.20%	1.31%	5.46%	-13.41%	-2.16%	7.08%	8.58%	0.12%	0.33%

Correlation

The correlation between FUMBX and FIBUX is 0.83, indicating a strong positive relationship between their price movements. Combining them offers limited diversification - they tend to fall together during downturns.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.83
Correlation (3Y) Calculated over the trailing 3-year period	0.84
Correlation (5Y) Calculated over the trailing 5-year period	0.85
Correlation (All Time) Calculated using the full available price history since Oct 20, 2017	0.82

The correlation between FUMBX and FIBUX has been stable across timeframes, ranging from 0.82 to 0.85 - a consistent structural relationship.

Return for Risk

FUMBX vs. FIBUX — Risk / Return Rank

Compare risk-adjusted metric ranks to identify better-performing investments over the past 12 months.

FUMBX

FUMBX Risk / Return Rank: 35
FUMBX Sharpe Ratio Rank: 30
FUMBX Sortino Ratio Rank: 38
FUMBX Omega Ratio Rank: 37
FUMBX Calmar Ratio Rank: 37
FUMBX Martin Ratio Rank: 33

FIBUX

FIBUX Risk / Return Rank: 21
FIBUX Sharpe Ratio Rank: 18
FIBUX Sortino Ratio Rank: 19
FIBUX Omega Ratio Rank: 17
FIBUX Calmar Ratio Rank: 27
FIBUX Martin Ratio Rank: 23

The rank (0–100) shows how this investment's returns compare to the risk taken. Higher = better. Based on the past 12 months of data, combining Sharpe, Sortino, and other metrics used by quantitative funds and institutional investors.

FUMBX vs. FIBUX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Short-Term Treasury Bond Index Fund (FUMBX) and Fidelity Flex U.S. Bond Index Fund (FIBUX). Risk-adjusted metrics are performance indicators that assess an investment's returns in relation to its risk, enabling a more accurate comparison of different investment options.

	FUMBX	FIBUX	Difference
Sharpe ratio Return per unit of total volatility	1.60	1.27	+0.34
Sortino ratio Return per unit of downside risk	2.58	1.89	+0.69
Omega ratio Gain probability vs. loss probability	1.32	1.23	+0.10
Calmar ratio Return relative to maximum drawdown	2.36	2.01	+0.35
Martin ratio Return relative to average drawdown	7.59	6.04	+1.55
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

FUMBX vs. FIBUX - Sharpe Ratio Comparison

The current FUMBX Sharpe Ratio is 1.60, which is comparable to the FIBUX Sharpe Ratio of 1.27. The chart below compares the historical Sharpe Ratios of FUMBX and FIBUX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Sharpe Ratios by Period

	FUMBX	FIBUX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.60	1.27	+0.34
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.44	0.01	+0.44
Sharpe Ratio (All Time) Calculated using the full available price history	0.73	0.35	+0.38

Drawdowns

FUMBX vs. FIBUX - Drawdown Comparison

The maximum FUMBX drawdown since its inception was -8.83%, smaller than the maximum FIBUX drawdown of -19.76%. Use the drawdown chart below to compare losses from any high point for FUMBX and FIBUX.

Drawdown Indicators

	FUMBX	FIBUX	Difference
Max Drawdown Largest peak-to-trough decline	-8.83%	-19.76%	+10.93%
Max Drawdown (1Y) Largest decline over 1 year	-1.54%	-2.97%	+1.43%
Max Drawdown (3Y) Largest decline over 3 years	-1.57%	-6.09%	+4.52%
Max Drawdown (5Y) Largest decline over 5 years	-8.60%	-18.40%	+9.80%
Current Drawdown Current decline from peak	-0.77%	-3.43%	+2.66%
Average Drawdown Average peak-to-trough decline	-1.86%	-5.79%	+3.93%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.48%	0.99%	-0.51%

Volatility

FUMBX vs. FIBUX - Volatility Comparison

The current volatility for Fidelity Short-Term Treasury Bond Index Fund (FUMBX) is 0.69%, while Fidelity Flex U.S. Bond Index Fund (FIBUX) has a volatility of 1.38%. This indicates that FUMBX experiences smaller price fluctuations and is considered to be less risky than FIBUX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	FUMBX	FIBUX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.69%	1.38%	-0.69%
Volatility (6M) Calculated over the trailing 6-month period	1.51%	2.86%	-1.35%
Volatility (1Y) Calculated over the trailing 1-year period	2.06%	4.03%	-1.97%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	2.92%	6.04%	-3.12%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	2.49%	5.12%	-2.63%

FUMBX vs. FIBUX - Expense Ratio Comparison

FUMBX has a 0.03% expense ratio, which is higher than FIBUX's 0.00% expense ratio. However, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.

Dividends

FUMBX vs. FIBUX - Dividend Comparison

FUMBX's dividend yield for the trailing twelve months is around 3.76%, less than FIBUX's 4.08% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017
FIBUX Fidelity Flex U.S. Bond Index Fund	4.08%	3.95%	3.65%	2.93%	1.62%	1.18%	2.32%	2.96%	2.70%	2.45%
FUMBX Fidelity Short-Term Treasury Bond Index Fund	3.76%	3.51%	2.91%	1.64%	0.86%	1.15%	1.41%	1.88%	1.64%	0.34%

Frequently Asked Questions

Can I hold both FUMBX and FIBUX in my portfolio?

FUMBX and FIBUX have a correlation of 0.83, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, FUMBX or FIBUX?

FIBUX has higher volatility (1.38%) compared to FUMBX (0.69%). In terms of maximum drawdown, FUMBX dropped -8.83% vs FIBUX's -19.76%.

Which has better risk-adjusted returns?

FUMBX currently has the higher Sharpe Ratio (1.60 vs 1.27), meaning it's delivered slightly more return per unit of risk over the trailing 12 months. However, this ranking shifts over time - use the Risk/Return Score above for a more comprehensive view that combines Sharpe, Sortino, and other measures used by quantitative funds.